Influence of additives on properties of sol-gel layers. Georgi, U.; Schlottig, F.; Graebner, H.; van Steensel, L.; Wolf, G.; Roewer, G.. Institute of Inorganic Chemistry, Freiberg University of Mining and Technology, Freiberg, Germany. J. Non-Cryst. Solids (2000), 277(2-3), 173-181.
Abstract
The addn. of glutardialdehyde, 3,4-dimethoxybenzaldehyde or aminocaproic acid enables a modification of the properties of the layers resulting from the sol-gel process of tetraethoxysilane (TEOS). Kinetics of various hydrolysis and condensation reaction steps were analyzed by ²⁹Si and ¹³C NMR spectroscopy. XPS studies give evidence that the additive mols. are also located on the surface. The layer morphol. was characterized by at. force microscopy.

Structure, Mobility, and Domain Sizes in Poly(chloromethylsilane-co-styrene). Brendler, E.; Jäger, Ch.; Scheller, D.; Roewer, G.. Institut fuer Analytische Chemie and Institut fuer Anorganische Chemie, Technische Universitaet Bergakademie Freiberg, Freiberg, Germany. Macromolecules (2000), 33(22), 8371-8374.
Abstract
The structure of poly(chloromethylsilane-co-styrene) obtained from polymn. of styrene and chloromethyldisilanes is investigated by HR liq. and solid-state NMR techniques. ¹H-¹³C DEPT and 1H-29Si HMBC investigations indicate that the system has to be considered as a polymer blend consisting of poly(chloromethylsilane) and polystyrene. Differences in the mobility of the two polymers are demonstrated by ¹H-¹³C WISE spectroscopy. The results of spin diffusion investigations carried out on poly(chloromethylsilane-co-styrene) samples indicate surprisingly small polystyrene domains.

Azomethine functionalized alkyltriethoxysilanes - precursors for thin silica layers. Georgi, U.; Görz, H.; Roewer, G.. Institute of Inorganic Chemistry, Freiberg University of Mining and Technology, Freiberg, Germany. Main Group Met. Chem. (2000), 23(7), 369-379.
Abstract
New alkyltriethoxysilanes, RCH:N(CH₂)₃Si(OEt)₃ (e.g., R = Ph, C₆H₄OH-2, C₆H₃(OH)₂-3,4) were synthesized by condensing aminopropyltriethoxysilane, NH₂(CH₂)₃Si(OEt)₃ with different aldehydes, RCHO. These polysiloxane precursors contg. an azomethine function enable layer prepn. via the sol-gel process. Their conversion were followed by ²⁹Si and ¹³C NMR spectroscopy. The layers were characterized by IR, ATR and XPS.

The effect of the electronic state of the educt silicon in the direct synthesis. Lorey, L.; Roewer, G.; Damm, C. Institute of Inorganic Chemistry, University of Mining and Technology Freiberg, Freiberg, Germany. Editor(s): Oeye, Harald A. Silicon Chem. Ind. V, [Conf.] (2000), 257-263. Publisher: Norwegian University of Science and Technology, Trondheim, Norway
Abstract
The usefulness of Photo-EMF measurements in order to characterize the educt silicon is discussed, showing the dependence of the selectivity and the amts. of disilanes in the crude silane mixt. on the conduction type (n- or p-type).

Formation of silicides in the system metal-silicon-chlorine-hydrogen: Consequences for the synthesis of trichlorosilane from silicon and hydrogen chloride. Acker, J.; Röver, I.; Roewer, G.; Bohmhammel, K. Department of Physical Chemistry, Freiberg University of Mining and Technology, Freiberg, Germany. Editor(s): Oeye, Harald A. Silicon Chem. Ind. V, [Conf.] (2000), 121-133. Publisher: Norwegian University of Science and Technology, Trondheim, Norway
Abstract
Raw silicon for the manufactory of trichlorosilane contains different transition metals, like Fe, Ni, Co, Ti, Mn, Cr and Cu. These elements are known to form stable silicide phases with different chem. behavior toward hydrogen chloride. Depending on the transition metal, different trichlorosilane and silicon tetrachloride yields are obtained, furthermore solid or volatile metal chlorides are formed. New results of thermodn. calcns. and kinetic investigations are presented to classify transition metal silicides and their influence on the reactivity of silicon with hydrogen chloride.

Formation and characterization of cyclic and polycyclic silthianes containing Si-Si bonds. Herzog, U.; Böhme, U.; Roewer, G.; Rheinwald, G.; Lang, H. Institut für Anorganische Chemie der TU Bergakademie Freiberg, Freiberg, Germany. J. Organomet. Chem. (2000), 602(1-2), 193-207.
Abstract
The reactions of several organochlorosilanes and -oligosilanes with H₂S and NEt₃ were investigated. Different bicyclic silthianes with bis-cyclopentyl, bicyclo-[3,3,0]-octane, bicyclo-[2,2,1]-heptane (norbornane), bicyclo-[3,2,1]-octane, bicyclo-[2,2,2]-octane and bicyclo-[3,2,1]-nonane skeletons were formed and characterized by MS and ¹H, ¹³C and ²⁹Si NMR. The reaction of 1,1,2,2-tetrachlorodimethyldisilane with H₂S and NEt₃ yields 1,3,5,7,9,11-hexamethyl-1,3,5,7,9,11-hexasila-2,4,6,8,10,12-hexathiatetracyclo[5.5.0^3,11.0^5,9]dodecane (4c) contg. three disilane units. D. functional theory calcns. proved the general observation that in compds. with Si₃S₂, five-membered rings are preferred. The crystal structures of 4c, 1,3,3,5,7,7-hexamethyl-1,3,5,7-tetrasila-2,4,6,8-tetrathiabicyclo[3.3.0]octane (6) and 1,2,2,4,4,5,6,6,8,8-decamethyl-1,2,4,5,6,8-hexasila-3,7-dithiabicyclo[3,3,0]octane (9) were detd.

Thermodynamics, kinetics and catalysis in the system Ni-Si-H-Cl: thermodynamic description of chlorine-containing silicides. Acker, Jorg; Bohmhammel, Klaus; Roewer, Gerhard. Institut fur Physikalische Chemie Technische Universitat Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. IV, [Lect. Poster Contrib. Muechner Silicontage], 4th (2000), Meeting Date 1998, 818-824. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
Transition metal silicides, contg. small amts. of chlorine, act as catalysts in the hydrodechlorination of silicon tetrachloride into trichlorosilane. Silicides, with comparable properties to the catalytically active phases, can be prepd. by the reaction of silicon-rich silicides with the resp. metal chloride. A thermodn. model of chlorine-contg. nickel silicides is given. Chlorine is considered to be dissolved in the silicides and is modeled as a lattice gas. Consequences regarding the bonding state of chlorine in the silicide phases are reported and discussed in relation to the interactions within the silicide lattice.

Salen-silicon complexes - a new type of hexacoordinate silicon. Haberecht, Jörg; Mucha, Frank; Böhme, Uwe; Roewer, Gerhard. Institut fur Anorganische Chemie Technische Universitat Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. IV, [Lect. Poster Contrib. Muechner Silicontage], 4th (2000), Meeting Date 1998, 500-504. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
The reaction of tetradentate azomethine ligands H₂salen* [N,N'-ethylene-bis(2-hydroxyacetophenoneimine)] or H₂salen.dbldag. [N,N'-ethylene-bis(3,5-di-tert-butyl-salicylideneimine)] with chlorosilanes produces Si compds. with hexacoordinated Si(salen)SiXY (X = Cl; Y = H, Cl, CH₃, C₆H₅). Both ligands X and Y can be exchanged for F. The crystal structure anal. of (salen*)SiF₂ reveals the truly hexacoordination of the Si atom. The chloro compds. (salen*)SiCl₂ undergo Wurtz-type coupling reactions leading to oligosilanes with hypervalent Si. Coupling of (salen*)SiCl₂ with acetylides creates compds. with an Si-C.tplbond.C-Si backbone.

29Si-MAS-NMR investigations of amino-substituted chloromethylpolysilanes. Brendler, E.; Trommer, K.; Roewer, G.. Institut fur Analytische Chemie Technische Universitat Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. IV, [Lect. Poster Contrib. Muechner Silicontage], 4th (2000), Meeting Date 1998, 372-377. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany CODEN: 68ZMAL Conference; General Review written in English. CAN 133:105064 AN 2000:349759
Abstract
The ²⁹Si-CP-MAS spectra of cured and noncured polysilane-co-styrene polymers are reported. Interpretation of the structural changes documented by the spectra was carried out using variable contact time and inversion recovery CP measurements for editing the spectra; the assignment of the signals is based on chem. shift ranges in oligosilanes. Using the data of model compds., chem. shifts in H-free ceramics can be estd. and used for interpretation of spectra as demonstrated for the system SiC_4-nN_n.

Base-catalyzed disproportionation of tetrachlorodimethyldisilane - investigations of the heterogeneous catalysts. Schulze, Norbert; Roewer, Gerhard. Institut fur Anorganische Chemie Technische Universitat Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. IV, [Lect. Poster Contrib. Muechner Silicontage], 4th (2000), Meeting Date 1998, 341-345. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
The disproportionation of 1,1,2,2-tetrachlorodimethyldisilane was carried out in the presence of various nitrogen donors grafted on silica. Apart from the steric influence, their nucleophilicity played an important role in the reaction. A -electron system or a low first ionization potential of the donor was not a necessary condition for the reaction. The catalysts were characterized by their sp. surface, loading and basicity.

Synthesis and characterization of new precursors based on organosilicon for construction of porous solid structures. Nitsche, S.; Weber, E.; Trommer, K.; Roewer, G.. Institut für Organische Chemie Technische Universität Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. IV, [Lect. Poster Contrib. Muechner Silicontage], 4th (2000), Meeting Date 1998, 312-316. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
The aim of this work consists in the gradual building up of a new class of porous precursors based on organosilicon chem. Therefore the rigid org. tecton 1,3,5-triethynylbenzene, 1,3,5-(RCº C)C₆H₃ (I; e.g., R = H, Li) was linked with various chloroaminosilanes, e.g., MeSiCl[SiMe(NEt₂)₂]₂ to give I (R = SiMe[SiMe(NEt₂)₂]₂). The amino functions of the aminosilane-substituted aryl acetylides were exchanged for Cl by treatment with HCl. These Si-Cl bonds allow further coupling and crosslinking reactions with bulky fragments to achieve a permanent cavity structure.

Synthesis of silicon synthons for a selective oligomer design. Trommer, K.; Herzog, U.; Roewer, G.. Institut für Anorganische Chemie Technische Universität Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. IV, [Lect. Poster Contrib. Muechner Silicontage], 4th (2000), Meeting Date 1998, 306-311. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
Amination of chlorosilanes with dialkylamine gave various chloro- and amino-substituted oligosilanes. The remaining reactive chloro sites enable to bond further functionalities as well as other silyl units to the silane. In this procedure the amino group is protecting potentially reactive sites at Si atoms and can be easily exchanged by chloro substituents. By this route a desired Si architecture can be built up.

Novel bis(1,2-N,N-dimethylaminomethylferrocenyl)silyl compounds. Palitzsch, Wolfram; Roewer, Gerhard; Pietzsch, Claus; Jacob, Klaus; Merzweiler, Kurt. Institut für Anorganische Chemie, TU Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. IV, [Lect. Poster Contrib. Muechner Silicontage], 4th (2000), Meeting Date 1998, 300-305. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
The treatment of SiCl₄ with two equiv. of 2-(dimethylaminomethyl)ferrocenyllithium [1; (FcN)Li] affords (FcN)₂SiCl₂ (2). The structure of 2 was detd. by x-ray diffraction anal. It was used as starting chlorosilyl compd. for reaction with Na[(h ⁵-C₅Me₄Et)Mo(CO)₃]. The reaction of 1 with 1,6-dichloro-dodecamethylhexasilane yields the novel (FcN)(SiMe₂)₆(FcN) (4).

Disilane fraction of the Müller/Rochow synthesis, a potential source for SiC ceramic precursors. Roewer, G.; Lange, Th.; Müller, E.; Martin, H.-P.; Richter, R.; Sartori, P.; Habel, W. TU Bergakademie Freiberg, Germany. Editor(s): Heinrich, Jürgen. Werkstoffwoche '98, Band VII: Symp. 9, Keram.; Symp. 14, Simul. Keram. (1999), Meeting Date 1998, 725-730. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
High-cross linked poly(methylchloro)silanes as cost-effective SiC precursors were prepd. by heterogeneous catalyzed disproportionation of tetrachlorodimethyldisilanes or other monosilanes. The copolymer poly(methylchloro)silane-co-styrene was obtained by addn. of styrene for adjustment the elastic- viscous properties. The green fiber SiC precursors can be manufd. by a melt-spinning procedure. Metal free ceramic SiC fibers with low O₂ content can be fabricated by pyrolysis at Ar atm.

Crystallization-controlled SiC fibers. Ade, M.; Martin, H.-P.; Kurtenbach, D.; Müller, E.; Knopf, C.; Rittmeister, B.; Roewer, G.; Brendler, E. Institut für Keramische Werkstoffe, TU Bergakademie Freiberg, Germany. Editor(s): Heinrich, Jürgen. Werkstoffwoche '98, Band VII: Symp. 9, Keram.; Symp. 14, Simul. Keram. (1999), Meeting Date 1998, 577-582. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
To improve both the long-term and thermal stability of polychloromethylsilanes-based SiC fibers a chem. stabilization of the amorphous state by transition metals and a control of the nanocryst. structure was attempted. By blends of zirconocene dichloride and polychloromethylsilane in styrene solvents an introduction of 1-3% stabilizing Zr dopants was achieved. The crystn. of the SiC fibers was controlled by crosslinking NH₃ addns. into the polymer precursors and thermal pretreatments at 800 °. The competing reaction of Si with N and the resulting overstoichiometric C led to a drastic decrease of crystn. rate and thus to a significant decrease of crystallite sizes after final crystn. at 1500 °C.

Synthesis of modified polycarbosilanes as precursors for very high temperature-resistant lightweight building materials. Sartori, P.; Habel, W.; Mayer, L.; Moll, A.; Windmann, T.; Roewer, G.; Herzog, U. Gerhard Mercator Universitat-GH-Duisburg, Germany. Editor(s): Heinrich, Jürgen. Werkstoffwoche '98, Band VII: Symp. 9, Keram.; Symp. 14, Simul. Keram. (1999), Meeting Date 1998, 465-470. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
A review on the synthesis of polycarbosilanes to be used as precursors for SiC and SiC/Al₂O₃ composites. Topics discussed include the synthesis of polycarbosilanes as precursors for SiC bodies, synthesis of the SiC ceramics, synthesis of polycarbosilanes as precursors for the synthesis of SiC fibers (Wurtz synthesis and subsequent reactions, Grignard variants), synthesis of SiC fibers from the precursors, properties of the SiC fibers, synthesis of Al₂O₃-SiC composites (synthesis of water-sol. polycarbosilanes), synthesis of Al₂O₃ composites from the precursors.

Development of a new type of SiC fiber. Müller, Eberhard; Martin, Hans-Peter; Roewer, Gerhard; Richter, Robin; Sartori, Peter; Habel, Wolfgang. TU Bergakademie Freiberg, Institut für Keramische Werkstoffe, Germany. Editor(s): Heinrich, Jürgen. Werkstoffwoche '98, Band VII: Symp. 9, Keram.; Symp. 14, Simul. Keram. (1999), Meeting Date 1998, 459-463. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
The disilane fraction, a cheap byproduct from the synthesis of chlorinated polysilanes, was used to produce polymeric precursors which, because of their unsatd. substituents, allow the preliminary photochem. curing of the green fibers. Addnl., the pyrolysis of these precursors was optimized so that the crystallinity of the SiC fibers which affects the mech. properties and the thermal stability could be controlled. The characteristics and the mech. properties of the SiC fibers synthesized in this way are discussed.

Crystal structure of N,N'-ethylenebis(3,5-di-tert-butylsalicylideneiminato)difluorosilane-dioxane (4/1), 4C₃₂H₄₆F₂N₂O₂Si*C₄H₈O₂. Haberecht, J.; Böhme, U.; Lang, H.; Roewer, G.; Rheinwald, G. Max-Planck-Institut Chemische Physik Fester Stoffe, Dresden, Germany. Z. Kristallogr. - New Cryst. Struct. (2000), 215(1), 135-137.
Abstract
The title compd. is triclinic, space group P1, a: 14.1657(2), b: 16.1074(2), c: 17.1227(1) Å, a : 89.4677(5), b : 65.9674(5), g : 79.0775(2) °, Z = 4, R = 0.058, Rw = 0.128 at T = 173 K for 10423 reflections with I_o > 2s (I_o). At. coordinates are given. The Si atom is octahedrally coordinated with salen acting as tetradentate ligand and 2 F atoms at the axial positions.

Synthesis and NMR investigations on butylthio-substituted mono- and oligosilanes. Herzog, U.; Roewer, G.. Institute of Inorganic Chemistry, University of Mining and Technology, Freiberg, Germany. Main Group Met. Chem. (1999), 22(10), 579-594.
Abstract
The complete series of monosilanes Me_xPhySiCl_4-x-y-z(SBu)_z was prepd. using the reaction of methylchlorosilanes with n-butylthiol and tri-ethylamine in n-hexane. All products were investigated by ¹H, ¹³C and ²⁹Si NMR. Trends of all important ¹H, ¹³C and ²⁹Si NMR parameters were correlated with changes in the substitution pattern. These investigations were expanded to a variety of methylchlorodi- and higher oligosilanes. In MeSi(SiCl₂Me)₃ only five of the six chlorine substituents could be replaced with HSBu/NEt₃ but MeSi(SiMe(SBu)₂)₃ could be isolated after treatment with BuSLi in THF.

Crystallization process of polysilane derived amorphous SiC. Kurtenbach, D.; Martin, H.-P.; Müller, E.; Roewer, G.; Kranold, R.; Höll, A.; Buhler, P.; Wild, M. J. Institute of Ceramic Materials, Freiberg University of Mining and Technology, Germany. Adv. Sci. Technol. (Faenza, Italy) (1999), 14(Ceramics: Getting into the 2000's, Pt. B), 285-292.
Abstract
Cl contg. polysilanes were synthetically produced from waste products from the Müller-Rochow-Synthesis. The polysilanes were fired under Ar to yield an amorphous Si-C ceramic material. To produce SiC-fibers the melt spun green fibers were cured by NH₃ as curing agent. The nucleation and crystn. process of both systems (Si-C and Si-N-C) were studied by XRD and small angle x-ray scattering (SAXS), He-pycnometry and detn. of SiC, free C, O₂ resp. N₂.

The complexes [Li(DIME)₂][W(CO)₅L] (I) [L = OCN, NCS, PPh₂, SiMe₂Ph, N(SiMe₃)₂, CH₂Ph, Si₆Me₁₁; DIME = diethylene glycol di-Me ether] were prepd. by reaction of [Li(DIME)₂][W(CO)₅I] with KOCN, KSCN, NaPPh₂, LiSiMe₂Ph, LiN(SiMe₃)₂, PhCH₂MgCl, and KSi₆Me₁₁, resp. Photochem. ligand substitution in W(CO)₆ was used as an alternative method for the prepn. of [K(DIME)₂][W(CO)₅NCS], [Na(DIME)₂][W(CO)₅N₃], [Li(DIME)₂][W₂(CO)₁₀(m -H)], and [K(DIME)₂][W₂(CO)₁₀(m -CN)] were synthesized in this manner. The crystal and mol. structure of I (L = Si₆Me₁₁) [Li(DIME)₂][W(CO)₅Si₆Me₁₁] was detd. by x-ray diffraction anal. (monoclinic, P2₁/n, a = 19.116(2), b = 14.308(2), c = 20.264(3) Å, b = 96.810(10) °, V = 4639.7(11) ų, Z = 4, r _c = 1.336 g/cm³, l (MoKa ) = 6.468 mm^-1, F(000) = 1912, 9517 independent reflections, 439 refined parameters, R₁ = 0.0575, wR₂ = 0.1453 (for I > 2s (I))). The spectral and chem. properties of all complexes are discussed. Pyrolysis of I (L = Si₆Me₁₁) leads to W silicide and W carbide.

Bis(1,2-N,N-dimethylaminomethylferrocenyl)dichlorosilane-structure and reactivity. Palitzsch, W.; Pietzsch, C.; Puttnat, M.; Jacob, K.; Merzweiler, K.; Zanello, P.; Cinquantini, A.; Fontani, M.; Roewer, G.. Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. J. Organomet. Chem. (1999), 587(1), 9-17.
Abstract
The treatment of SiCl₄ with two equiv. of 2-dimethylaminomethylferrocenyllithium (1), (FcN)Li, affords (R,S)-(FcN)₂SiCl₂ (3). Complex 3 was used as the starting chlorosilyl compd. for reaction with MeMgCl to give (R,S)-(FcN)₂SiMe₂ (4). Dimethyldichlorosilane reacts with two equiv. of 1 to form an isomeric mixt. of 4 (meso) and (R,R)- and (S,S)-bis(1,2-N,N-dimethylaminomethylferrocenyl)dimethylsilane. A detailed characterization of 3 and 4 was carried out by ¹H-, ¹³C-, ²⁹Si-NMR and Mössbauer spectroscopies. The structures of 3 and 4 were detd. by x-ray diffraction anal. The redox behavior of 3 and 4 was studied by electrochem. techniques.

Template synthesis of SiO₂ nanostructures. Schlottig, F.; Textor, M.; Georgi, U.; Roewer, G.. Laboratory for Surface Science and Technology, Department of Materials, ETHZ, Zurich, Switz. J. Mater. Sci. Lett. (1999), 18(8), 599-601.
Abstract
There are different concepts of using the pores in nanoporous membranes as templates for prepg. nanomaterials. In this study, the versatile silica-based system and the dip- and spin-coating technique were used to prep. nano-structured SiO₂ samples by the template method. Com. porous alumina membranes with three different pore sizes (nominally with diams. of 0.2, 0.1 and 0.02 m m) were used as a template material. Sol-gel systems with a relatively fast gelation rate were used for the pore-filling procedure. In the first step, tetraethoxysilane, ethanol, water and HCl were mixed in three different molar ratios and stirred for 3 h at room temp. The pores of the alumina membranes were filled using both spin- and dip-coating procedures. After a partial removal of the alumina (5 min in NaOH) from the coated membrane, an array of closed SiO₂ tubules was obsd. On the other hand, the complete removal of the membrane (10 min in NaOH) leads to an array of open SiO₂ nanotubules. In comparison to glass, the gel structure shows smaller line-widths and therefore greater order.

Modification of the base-catalyzed disproportionation of methylchlorodisilanes. Herzog, U.; Schulze, N.; Trommer, K.; Roewer, G.. Department of Chemistry, University of Wisconsin, Madison, WI, USA. Main Group Met. Chem. (1999), 22(1), 19-33.
Abstract
The product range of the base-catalyzed disproportionation of methylchlorodisilanes, esp. 1,1,2,2-tetrachlorodimethyldisilane, can be modified by adding phenyltrichlorosilane to obtain Ph contg. polysilanes. The first formed Ph substituted oligomers up to a tetrasilane and some further derivs. could be prepd. on different synthetic routes, too. Silylstannane formation as well as a redn. to elemental tin result from the co-disproportionation of 1,1,2,2-tetrachlorodimethyldisilane and methylchlorostannanes whereas SnCl₄ reacts quant. to SnCl₂ and GeCl₄ gives a germanium subchloride. The disproportionation can be applied to 1,1,2,2-tetrafluorodimethyldisilane instead of the chloro compd. and yields a branched methylfluoropolysilane as an oily residue besides MeSiF₃.

Sol-gel immobilized glucose-oxidase: calorimetric investigations of enzyme activities. Georgi, U.; Gräbner, H.; Roewer, G.; Wolf, G. Institute of Inorganic Chemistry, Freiberg University of Mining and Technology, Freiberg, Germany. J. Sol-Gel Sci. Technol. (1998), 13(1/2/3), 295-298.
Abstract
Using the sol-gel process, the enzyme glucose-oxidase was immobilized in modified SiO₂ layers. The tetraethoxysilane based sol was varied by veratrylaldehyde, aminopropyltriethoxysilane and an azomethine compd., which was synthesized from both mols. Changes in reaction kinetics of the sol-gel process by addn. of veratrylaldehyde were obsd. by 29Si NMR measurements. The fixation of this additive in the final gel was clarified by FTIR spectroscopy. The influence of inserted functional groups on the enzyme activity was detd. by calorimetry. The Enzyme Thermistor is a fast and uncomplicated method to obtain comparative results of sol-gel immobilized enzyme activity. Differences in immobilization effects were found dependent on structure and concn. of additives.

Hexacoordinate silicon-azomethine complexes. Synthesis, characterization, and properties. Mucha, Frank; Haberecht, Jörg; Böhme, Uwe; Roewer, Gerhard. Institut Anorganische Chemie, Technische Universität Bergakademie, Freiberg, Germany. Monatsh. Chem. (1999), 130(1), 117-132.
Abstract
N,N'-ethylenebis(2-hydroxyacetophenoneimine) = salen*H₂ and N,N'-ethylenebis(3,5-di-tert-butylsalicylideneimine) = salen⁺H₂ react both with SiCl₄ under formation of hexacoordinate Si compds. ((salen')SiCl₂, salen' = salen* or salen⁺). The analogous fluoro derivs. (salen')SiF₂ were prepd. by reaction of (salen')SiCl₂ with ZnF₂. X-ray structure anal. of (salen*)SiF₂ clearly demonstrates the octahedral coordination of Si salen* acts as a tetradentate chelating ligand, 2 halogen atoms remaining at the Si atom. The redn. of (salen*)SiCl₂ by alk. metal affords polysilanes contg. main chain hexacoordinate Si. Coupling with acetylides results in polycarbosilanes with a Si-Cº C-Si backbone.

Chances for the use of SiC fibers in thermal plants. State-of-the-art. Martin, H.-P.; Müller, E.; Roewer, G.. Inst. f. Keramische Werkstoffe, TU Bergakad. Freiberg, Freiberg, Germany. Freiberg. Forschungsh. A (1998), A848 (Einsatz Neuer Keramischer Materialien in Thermischen Anlagen), 79-94.
Abstract
A review including discussion of the types of fibers, manufg. methods (CVD, polymer route, spinning, cellulose-precursor fibers), the properties of com. available SiC-based fibers, the more cost-effective SiC fibers manufd. by the Freiberg method and their properties, as well as the use of SiC fibers in thermal plants.

Crystallization of polymer derived silicon carbide materials. Kurtenbach, D.; Martin, H. -P.; Müller, E.; Roewer, G.; Höll, A. Institute Ceramic Materials, Freiberg University Mining & Technology, Freiberg, Germany. J. Eur. Ceram. Soc. (1998), 18(13), 1885-1891.
Abstract
Silicon carbide fibers are produced by melt spinning of chlorine contg. polysilanes under argon and cross linked by application of ammonia as curing agent and finally pyrolyzed. Their thermal behavior is investigated. The crystn. process with increasing pyrolysis temp. is characterized by X-ray diffraction (XRD) and small angle X-ray scattering (SAXS). Oxygen, nitrogen and free carbon contents are detd. and combined with d. measurements to obtain information about the microstructure of the system. The comparison of non-cured systems (Si-C) and cured materials (Si-N-C) gives insight into the high-temp. processes. Investigations concerning the nucleation mechanism are further carried out and were described in detail.

Reactivity of transition metal silicides towards silicon tetrachloride/haloalkanes and hydrogen. Roewer, G.; Werkmeister, J.; Bohmhammel, K. Institut of Inorganic Chemistry, Freiberg University of Mining and Technology, Freiberg, Germany. Editor(s): Oeye, Harald A. Silicon Chem. Ind. IV, [Conf.] (1998), 239-252. Publisher: Norwegian University of Science and Technology, Trondheim, Norway
Abstract
Metal silicides M_nSi_m (M = Ni, Co, Fe, Cu, Pt) can be formed either via reaction of SiCl₄/H₂ mixts. with dispersed metals or by reaction of metal halides with silicon. Such intermetallic silicide phases are able to catalyze hydrodehalogenation reactions of silicon tetrachloride or haloalkanes. They react also with chlorofluorocarbons as CCl₂F₂, C₂Cl₃F₃, C₂Cl₂F₄, giving haloolefins, halosilanes and some byproducts. Mechanisms of these processes are strongly related to Müller/Rochow Synthesis.

Thermodynamic and kinetic study of the Ni-Si-Cl-H-system: the relevance for the catalytic synthesis of trichlorosilane. Acker, J.; Bohmhammel, K.; Roewer, G.. Department of Physical Chemistry, Freiberg University of Mining and Technology, Freiberg, Germany. Editor(s): Oeye, Harald A. Silicon Chem. Ind. IV, [Conf.] (1998), 133-143. Publisher: Norwegian University of Science and Technology, Trondheim, Norway
Abstract
Transition metal silicides are known as catalysts for the hydrodehalogenation of silicon-tetrachloride to trichlorosilane. The model reaction NiSi_x + NiCl₂ allows the study of the main reactions of the catalytic process in a convenient way. The crucial step is the formation of a silicide based chlorine contg. surface phase. This surface phase enables the fast moving of silicon in the bulk silicide, resulting in SiCl₂ species at the surface. This process is accompanied by a phase transformation in the bulk silicide. Thermodn. calcns. and kinetic models are applied to understand single steps of the complex reaction course and the formation sequences of the products. A mechanism of the reactions is proposed.

Generation and investigation of various [(alkylamino)phenylsilyl]lithium species. Behavior in coupling reactions with chlorosilanes. Trommer, K.; Herzog, U.; Georgi, U.; Roewer, G.. Inst. Anorganische Chem., Technische Univ. Bergakademie, Freiberg, Germany. J. Prakt. Chem./Chem.- Ztg. (1998), 340(6), 557-561.
Abstract
Cl₂Ph(Et₂N)Si, ClPh(Et₂N)₂Si, [ClPh(Et2N)Si]₂, and Cl(Et₂N)PhSiSiPh(NEt₂)₂ were synthesized. ClPh(Et₂N)₂Si and Cl(Et₂N)PhSiSiPh(NEt₂)₂ react with Li powder to form the corresponding silyllithium compds. The resulting species were characterized in soln. by ¹³C and ²⁹Si NMR. To prove the expected substitution patterns of the silyllithium compds. some coupling reactions with chlorosilanes were carried out and the resulting new oligosilanes were characterized by NMR and mass spectrometry.

First Crystal Structure of a Cyclohexasilyl Transition-Metal Derivative, [(DIME)₂Li][Mo(CO)₅Si₆Me₁₁] (DIME = Diethylene Glycol Dimethyl Ether). Palitzsch, Wolfram; Böhme, Uwe; Beyer, Christian; Roewer, Gerhard. Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. Organometallics (1998), 17(14), 2965-2969.
Abstract
The reaction of [(DIME)₂Li][Mo(CO)₅I] with KSi₆Me₁₁ affords [(DIME)₂Li][W(CO)₅Si₆Me₁₁]. Its crystal structure and chem. properties are discussed.

1,2-N,N-dimethylaminomethylferrocenyl as a ligand towards silicon. Palitzsch, Wolfram; Pietzsch, Claus; Jacob, Klaus; Edelmann, Frank T.; Gelbrich, Thomas; Lorenz, Volker; Puttnat, Mark; Roewer, Gerhard. Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Leipziger Strasse 29, Freiberg/Sa, Germany. J. Organomet. Chem. (1998), 554(2), 139-146.
Abstract
The restudy of reactions of [2-(dimethylaminomethyl)ferrocenyl]lithium (1), (FcN)Li, with SiCl₄ or Me₃SiCl gave (FcN)SiCl₃ (2) and (FcN)SiMe₃ (3), resp.; 2 is an orange-red solid, but previously was reported as a red liq. The structure of 2 was detd. by x-ray structure anal. The reaction of 2 with NaOCHMe₂ yields the novel compd. (FcN)Si(OCHMe₂)₃ (4) which was subjected to x-ray diffraction anal. as its hydrochloride 4*HCl (5). Treating 1 with Cl(SiMe₂)₆Cl gave 82% (FcN)(SiMe₂)₆(FcN) (6).

Synthesis and characterization of new disilane derivatives of tungsten. Palitzsch, Wolfram; Böhme, Uwe; Roewer, Gerhard. Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. J. Organomet. Chem. (1998), 552(1-2), 213-219.
Abstract
Using salt elimination, (h ⁵-C₅Me₄Et)W(CO)₃SiMe₂SiMe₂R (R = Me, Cl, Br), (h ⁵-C₅Me₄Et)W(CO)₃SiMe₂SiMe₂(h ⁵-C₅Me₄Et)W(CO)₃, (h ⁵-C₉H₇)W(CO)₃SiMe₂SiMe₂Cl (C₉H₇ = indenyl) and (h ⁵-C₉H₇)W(CO)₃SiMe₂SiMe₂(h ⁵-C₉H₇)W(CO)₃ were prepd. and characterized. A hydridotris(3,5-dimethylpyrazolyl)borate (Tp*) stabilized W disilane complex, Tp*W(CO)₂SiMe₂SiMe₂Cl, was prepd. by novel one pot synthesis, isolated and characterized.

Preparation and NMR spectroscopical investigations of (diethylamino)(methoxy)-methylchlorodi- and -trisilanes. Herzog, U.; Trommer, K.; Roewer, G.. Institut für Anorganische Chemie, TU Bergakademie Freiberg, Freiberg, Germany. J. Organomet. Chem. (1998), 552(1-2), 99-108.
Abstract
Starting from the methylchlorodisilanes SiClMe₂-SiClMe₂, SiCl₂Me-SiCl₂Me and methylchlorotrisilanes SiClMe₂-SiClMe-SiClMe₂ and SiCl₂Me-SiClMe-SiCl₂Me the stepwise reaction with first HC(OMe)₃/[AlCl₃] and second HNEt₂ gives (diethylamino)(methoxy)-methylchlorooligosilanes. The products were studied by ²⁹Si, ¹H NMR spectroscopy and GC/MS measurements.

Azomethine-substituted organotrialkoxysilanes and polysiloxanes. Mucha, Frank; Roewer, Gerhard. Inst. Anorg. Chem., Tech. Univ. Bergakad. Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. III, [Muench. Silicontage], 3rd (1998), Meeting Date 1996, 400-402. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
During the last few years intense research has been focussed on the elaboration of synthetic materials based on modified silicon esters. Products with interesting properties were formed by synthesis of a novel group of derived silicon esters. The condensation of carbonyl- and amino groups leads to organotrialkoxysilanes contg. azomethine bonds. From these compds. three-dimensional, cross-linked silicon polymers were synthesized by hydrolysis/condensation.

Selective hydrogenation of methylchlorooligosilanes. Herzog, Uwe; Roewer, Gerhard. Inst. f. Anorg. Chem., Tech. Univ. Bergakad. Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. III, [Muench. Silicontage], 3rd (1998), Meeting Date 1996, 312-316. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
Using a base-catalyzed hydrogenation of methylchlorooligosilanes (Si₃-Si₆) with trialkylstannanes, partially hydrogenated methylchlorooligosilanes can be prepd. and identified by ²⁹Si and ¹H NMR spectroscopy. Starting from methylchlorosilanes like SiClMe₂SiClMeSiClMe₂ certain partially hydrogenated compds. can be prepd. selectively because of the different reactivity of the Si-Cl bonds towards hydrogenation by R₃SnH.

Disproportionation of chloromethyldisilanes using Lewis base heterogeneous catalysts - a way to influence the polymer structure. Lange, Thomas; Schulze, Norbert; Roewer, Gerhard; Richter, Robin. Inst. f. Anorg. Chem., Tech. Univ. Bergakad. Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. III, [Muench. Silicontage], 3rd (1998), Meeting Date 1996, 291-295. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
The heterogeneous disproportionation of 1,1,2,2-tetrachlorodimethyldisilane to chloromethylsilanes and oligo(chloromethylsilane)s is catalyzed by Lewis bases like bis(dimethylamido)phosphoryl compds. and N-heterocycles. The oligosilanes undergo branching and crosslinking reactions controlled by temp. and time, forming poly(chloromethylsilane)s that show a 3D polysilyne-type skeleton. Lewis acids, such a triphenylboron, dissolved in the starting disilane, prevent branching of the polymer backbone during the reaction.

New transition metal substituted oligosilanes. Palitzsch, Wolfram; Böhme, Uwe; Roewer, Gerhard. Inst. f. Anorg. Chem., Tech. Univ. Bergakad. Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. III, [Muench. Silicontage], 3rd (1998), Meeting Date 1996, 262-266. Publisher: Wiley-VCH Verlag GmbH, Weinheim, Germany
Abstract
The transition metal substituted disilanes (h ⁵-C₅Me₄Et)Fe(CO)₂SiMe₂SiMe₂Cl and (h ⁵-C₅Me₄Et)Mo(CO)₃SiMe₂SiMe₂Br were prepd. by salt elimination. Both compds. are well crystd. and their structures detd. by x-ray diffraction anal. Surprisingly, the reaction of Na[(h ⁵-C₅Me₄Et)Fe(CO)₂] with Br(SiMe₂)₆Br gave exclusively the diiron hexasilane complex (h ⁵-C₅Me₄Et)(CO)₂Fe(SiMe₂)₆Fe(CO)₂(h ⁵-C₅Me₄Et).

Freiberg (Germany) SiC fibers. True state of development. Martin, Hans Peter; Müller, Eberhard; Roewer, Gerhard; Richter, Robin. Institut Keramische Werkstoffe, TU Bergakademie Freiberg, Freiberg, Germany. Chem.-Ing.-Tech. (1998), 70(1-2), 170-173.
Abstract
The method developed in the University of Freiberg (Germany) for the synthesis of SiC fibers is described. A polysilane polymer is spun and then cured by crosslinking with NH₃ in Ar under the exclusion of moisture and O₂ to produce an infusible polymer fiber. These fibers are subsequently pyrolyzed at 1200-1300 °C to produce essentially amorphous SiC that contains crystallites of 1-2 nm. The thermal stability and mech. properties of these fibers are described.

Silicon carbide fibers from Freiberg. The real state of development. Martin, Hans Peter; Müller, Eberhard; Roewer, Gerhard; Richter, Robin. Department Ceramic Materials, University Mining Technology, Freiberg, Germany. Chem. Eng. Technol. (1998), 21(1), 48-50.
Abstract
A review on SiC fibers from Freiberg in Germany is given. The manufg. is described as well as some advantages of this type of polymer route. SiC fibers showed high tensile strength and temp. stability. Focus is given on the curing step. Possible applications include their use as a composite component for ceramic matrix materials, filtration, and thermal insulation equipment.

Properties of silicon carbide fibers made from chlorine-containing polysilanes. Martin, H.-P.; Müller, E.; Richter, R.; Roewer, G.. TU Bergakademie Freiberg, Freiberg, Germany. Editor(s): Ziegler, G. Werkst.- Verfahrenstech., Symp. 6, Werkstoffwoche '96 (1997), Meeting Date 1996, 885-890. Publisher: DGM Informationsgesellschaft, Oberursel, Germany
Abstract
Silicon carbide fibers were prepd. by thermal treatment of chlorine-contg. polysilanes, which are derived by catalytic disproportionation of the so-called disilane fraction, a byproduct from silicon manuf. Following an initial pyrolysis, heat treatment of the resulting fibers results in low-oxygen-content (<0.9 wt.%) fibers. The mech. properties (i.e., a low mech. strength) can be improved by incorporating other processes (such as spinning, crosslinking, etc.). The fibers are thermally stable up to 1400 °C, during which a SiO₂ protective layer is formed, which decreases the fiber mech. properties.

SiC fibers from silicon chemical-industry byproducts. Martin, H.-P.; Müller, E.; Lange, Th.; Roewer, G.. Inst. Keramischen Werkstoffe, TU Bergakademie Freiberg, Freiberg, Germany. Editor(s): Leonhardt, G.; Wielage, B. Recycl. Verbundwerkst. Werkstoffverbunden (1997), 119-123. Publisher: DGM Informationsgesellschaft, Oberursel, Germany
Abstract
The disilane fraction from the Mueller-Rochow synthesis of methylchlorosilanes [of general formula (CH₃)_xSi₂Cl_6-x (x = 2-6)] was subjected to catalytic disproportionation to yield monomeric methylchlorosilanes and chlorine-contg. polysilanes. The chlorine-contg. polysilanes can then be used as a raw material for the prodn. of silicon carbide ceramic fibers.

Reaction of the Si-Cl bond with trialkyl orthoformates. Preparation of alkoxy-substituted silanes. Herzog, U.; Schulze, N.; Trommer, K.; Roewer, G.. TU Bergakademie Freiberg, Institut für Anorganische Chemie, Freiberg, Germany. J. Organomet. Chem. (1997), 547(1), 133-139.
Abstract
Trialkyl orthoformates in the presence of AlCl₃ represent quite useful reagents to generate Si alkoxides from chlorosilanes. 3-Cyanopropyltrichlorosilane and 2-[(2-trichlorosilyl)ethyl]-pyridine give the triethoxy compds. 3-cyanopropyltriethoxysilane and 2-[(2-triethoxysilyl)ethyl]-pyridine, resp. Via this route, in methylchlorooligosilanes a partial or complete exchange of the Cl substituents for alkoxy groups occurs depending on the starting molar ratio of silane:HC(OR)₃ (R = Me, Et). SiCl₂Me groups react to SiClMe(OR) first before SiMe(OR)₂ groups are formed. (Si)₂SiClMe units are not affected by HC(OR)₃.

Preparation and ²⁹Si NMR spectroscopic investigations of (diethylamino)methylchlorotetra- and -pentasilanes. Trommer, Kristin; Herzog, Uwe; Roewer, Gerhard. Inst. für Anorganische Chemie, TU Bergakademie, Freiberg, Germany. J. Prakt. Chem./Chem.- Ztg. (1997), 339(7), 637-641. CODEN: JPCCEM ISSN: 0941-1216. Journal written in English. CAN 128:3721 AN 1997:675411
Abstract
The treatment of several branched methylchlorooligosilanes (Si₄, Si₅) with Et₂NH leads to a partial or complete substitution of the chloro substituents for Et₂N groups with formation of the first known (diethylamino)(methyl)chlorooligosilanes contg. more than two Si atoms. Condensation reaction of (Et₂N)₂MeSiSi(NEt₂)(Me)Cl with Li in THF yields the linear tetrasilane Et₂N[SiMe(NEt₂)]₄NEt₂. The NMR studies provided information of the general shift ranges of several Si units in (diethylamino)(methyl)chlorooligosilane systems as well as the no. of stereoisomers of the prepd. products.

Preparation and characterization of oligomeric as well as polymeric ethynylsilanes containing Si₂-Si₄ units. Herzog, U.; Roewer, G.; Moll, A.; Habel, W.; Windmann, T.; Sartori, P. Institut für Anorganische Chemie, TU Bergakademie, Freiberg, Germany. J. Prakt. Chem./Chem.- Ztg. (1997), 339(7), 603-606.
Abstract
The treatment of methylchlorodisilanes with BrMgCº CMgBr resulted in oligomeric as well as polymeric ethynyldisilanes. The type of the product is related to the chloro functionality of the starting disilane. The reaction of SiClMe(SiCl₂Me)₂ as well as SiMe(SiCl₂Me)₃ yielded polymers beside small amts. of the monomeric products (HCº C)MeSi[SiMe(Cº CH)₂]₂ and MeSi[SiMe(Cº CH)₂]₃.

Preparation of oligosilanes containing perhalogenated silyl groups (-SiX₃, -SiX₂-, SiX-, X = Cl, Br) and their hydrogenation by stannanes. Herzog, U.; Roewer, G.. Institut für Anorganische Chemie, TU Bergakademie Freiberg, Leipziger Strasse 29, D-09596, Freiberg, Germany. J. Organomet. Chem. (1997), 544(2), 217-223.
Abstract
Starting from Me Ph substituted oligosilanes the disilanes SiX₃-SiXiMe_3-i (i = 0, 1, 2; X = Cl, Br), trisilanes SiX₂(SiX_iMe_3-i) (i = 0, 1) and branched tetrasilanes SiX(SiXMe₂)₃ were synthesized and their behavior towards the Lewis-base catalyzed hydrogenation by stannanes was studied. In the case of methylchlorodisilanes SiCl₃-SiCl_iMe_3-i Si-Si bond cleavage competes with the hydrogenation reaction.

Crystallization of polymer-derived silicon carbide fibers. Martin, H. P.; Kurtenbach, D.; Müller, E.; Roewer, G.. Inst. Ceramic Materials, Freiberg Univ. Mining Technology, Freiberg, Germany. Key Eng. Mater. (1997), 132-136(Pt. 3, Euro Ceramics V), 1958-1961.
Abstract
Amorphous (compn. is given) SiC fibers were prepd. by melt spinning of polysilane. They were optionally cured at 220 °C and pyrolyzed at 1000-1500 °C. Crystn. behavior was monitored using XRD, small angle scattering, NMR, thermogravimetry, and d. measurements. Structural ordering proceeded already after pyrolysis at 1000 °C, but it was not obvious that this effect was stretched over large areas. Crystn. was found at >1400 °C due to destruction of the fibers by cleavage of N and crystallite growth.

Manufacture of optionally heteroatom-containing polycarbosilane-type compounds suitable for manufacturing low-oxygen silicon carbide fibers. Habel, Wolfgang; Moll, Andre; Oelschlaeger, Andreas; Sartori, Peter; Windmann, Thomas; Martin, Hans-Peter; Richter, Robin; Roewer, Gerhard. (Habel, Wolfgang, Germany; Moll, Andre; Oelschlaeger, Andreas; Sartori, Peter; Windmann, Thomas; Martin, Hans-Peter; Richter, Robin; Roewer, Gerhard). Ger. Offen. (1997), 9 pp., Patent written in German. Application: DE 95-19545217 19951205.
Abstract
The Si-org. compds. contain structural repeating units selected from -ASi(R1)2Si(R1)2A-, -ASi(R1)(A1)Si(R1)2A-, and -ASi(R1)(A1)Si(R1)(A1)A- (same or different, R1 = H, alkyl, cycloalkyl, aryl, alkylarene, alkenyl, and alkynyl, preferably Me). These compds. can be spun, and the green fibers stabilized by simple method without use of reactive gases. Polycarbosilane fibers were manufd. from, e.g., a ethyne-bis(chlorodimethyl)disilane-chlorodimethyl-dichloromethyl disilane-bis(dichloromethyl)disilane copolymer.

New olefinic functionalized disilanes. Synthesis and NMR spectroscopical investigations. Trommer, K.; Herzog, U.; Roewer, G.. Institut für Anorganische Chemie Technische Universität Bergakademie Freiberg, Leipziger Str. 29, D-09596, Freiberg, Germany. J. Organomet. Chem. (1997), 540(1-2), 119-125.
Abstract
The new olefinic substituted aminodisilanes, RSi(NEt₂)MeSiR'(NEt₂)Me (I; R = R' = CH₂CH=CH₂, CH=CH₂; R = NEt₂, R' = CH₂CH=CH₂, CMe=CH₂, CH=CH₂) which were obtained from the reaction of organometallic reagents (e.g., RMgBr) with aminochlorodisilanes (e.g., I, R, R' = Cl), are converted into the chlorodisilanes, RSiMeClSiR'MeCl, by equilibration reactions or treatment with HCl. The resulting olefinic functionalized disilanes are identified by ²⁹Si, ¹³C, ¹H NMR and GC MS measurements.

Synthesis and characterization of new oligosilane derivatives of iron and molybdenum. Palitzsch, Wolfram; Böhme, Uwe; Roewer, Gerhard. Technische Universität Bergakademie Freiberg, Institut für Anorganische Chemie, Leipziger Strasse 29, D-09596, Freiberg, Germany. J. Organomet. Chem. (1997), 540(1-2), 83-88.
Abstract
Using salt elimination, the transition metal substituted oligosilanes (h ⁵-C₅Me₄Et)Fe(CO)₂SiMe₂SiMe₂Cl (1), (h ⁵-C₅Me₄Et)Mo(CO)₃SiMe₂SiMe₂Br, (h ⁵-C₅Me₄Et)Fe(CO)₂(SiMe₂)₆(CO)₂Fe(h ⁵-C₅Me₄Et) and (h ⁵-C₅Me₄Et)Fe(CO)₂(SiMe₂)₆Br were prepd. and characterized. Compd. 1 is crystd. well from pentane and its structure was detd. by x-ray diffraction analysis.

1,4-Addition of 1,1,2,2-tetrachlorodimethyldisilane to 1,4-diaza-1,3-dienes. Synthesis and molecular structure of 1,6-disila-2,5-diaza-1,1,6,6-tetrachloro-1,6-dimethyl-2,5-di-p-tolyl-3,4-diphenylhex-3-ene. Herzog, U.; Roewer, G.; Ziemer, B.; Herrschaft, B. Institut für Anorganische Chemie der TU Bergakademie Freiberg, Leipziger Str. 29, D-09596, Freiberg, Germany. J. Organomet. Chem. (1997), 533(1-2), 73-77.
Abstract
Reaction of 1,1,2,2-tetrachlorodimethyldisilane with 1,4-diazadienes like benzildianil, benzildi-p-tolil and benzildi-p-anisil leads to a 1,4-addn. product of the disilane with cleavage of the Si-Si bond. The structure of cis-p-MeC₆H₄N(SiCl₂Me)C(Ph)=C(Ph)N(SiCl₂Me)C₆H₄Me-p (I) was detd. by X-ray crystallog. (crystal data: monoclinic, P2₁/n, a = 14.661(4), b = 12.283(2), c = 17.564(5) Å, b = 103.13 °, Z = 4, R = 0.0585 for 5992 independent reflections). Surprisingly, I was in the cis-configuration with almost C2 symmetry and a torsion angle of only 13 °. Owing to statistical disorder, some bond lengths are not in the expected range.

[Li(dime)₂][W(CO)₅I] as a novel synthon for the preparation of silyl, amino and organyl derivatives of pentacarbonyl tungsten (dime = diethylene glycol dimethyl ether). Palitzsch, W.; Böhme, U.; Roewer, G.. Institut für Anorganische Chemie der TU Bergakademie Freiberg, Freiberg, Germany. Chem. Commun. (Cambridge) (1997), (8), 803-804.
Abstract
The one-pot reactions of M(CO)₆ with dime in the presence of LiIEt₂O give [Li(dime)₂][M(CO)₅I] (M = W 1, Mo). The reaction of 1 with LiSiMe₂Ph, LiN(SiMe₃)₂ and PhCH₂MgCl affords [Li(dime)₂][W(CO)₅R] [R = SiMe₂Ph, N(SiMe₃)₂, CH₂Ph]. The crystal structure of 1 was detd. [monoclinic, space group P2₁/c, Z = 4, R = 0.0772, Rw = 0.0970].

Chemical modification of thin silica films via the sol-gel-process. Georgi, U.; Brendler, E.; Görz, H.; Roewer, G.. Institute of Inorganic Chemistry, Freiberg University of Mining and Technology, Freiberg, Germany. J. Sol-Gel Sci. Technol. (1997), 8(1/2/3), 507-509.
Abstract
The sol-gel technique was used for the prepn. of silica films. The properties of these layers were varied by modification with aliph. and arom. compds. contg. carbonyl groups. Structural changes in the gels were obsd. by IR and MAS NMR spectroscopy. The incorporated org. compds. interact weakly with the gel matrix, forming hydrogen bridges.

29Si NMR investigations on oligosilane dendrimers. Herzog, U.; Notheis, C.; Brendler, E.; Roewer, G.; Thomas, B. Institut für Analytische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. Fresenius' J. Anal. Chem. (1997), 357(5), 503-504.
Abstract
Several octa- and decasilane dendrimers, prepd. starting from SiClMe(SiCl₂Me)₂ and SiMe(SiCl₂Me)₃, contg. directly neighboring branchings were studied by ²⁹Si NMR. In these compds. the ²⁹Si chem. shifts of the different silyl groups are shifted towards lower field compared with those of analogous groups in tetra- or hexasilanes.

Conversion process of chlorine containing polysilanes into silicon carbide. Part I. Synthesis and crosslinking of poly(chloromethyl)silanes-carbosilanes and their transformation into inorganic amorphous silicon carbide. Martin, H.-P.; Müller, E.; Richter, R.; Roewer, G.; Brendler, E. Institutes of Ceramic Materials, Inorganic Chemistry and Analytical Chemistry, Freiberg University of Mining and Technology, Freiburg, Germany. J. Mater. Sci. (1997), 32(5), 1381-1387.
Abstract
Synthesis of chlorine- contg. polysilanes by catalytic redistribution is described and the obtained polymers are characterized by IR- and magic angle spinning NMR (MAS-NMR) spectroscopy and elemental anal. The pyrolysis of such polysilanes was investigated by thermoanal., IR-, MAS NMR- and ESR spectroscopy. The conversion process from polysilane into polycarbosilane is described in terms of the results of the performed investigations and a model of the process is developed. Differences between this conversion process and those for chlorine-free polysilanes or polycarbosilanes previously described by other authors are discussed.

Organosilicon polymers-synthesis, architecture, reactivity and applications. Richter, Robin; Roewer, Gerhard; Böhme, Uwe; Busch, Kathleen; Babonneau, Florence; Martin, Hans Peter; Müller, Eberhard. Department of Inorganic Chemistry, Freiberg University of Mining and Technology, Freiberg, Germany. Appl. Organomet. Chem. (1997), 11(2), 71-106.
Abstract
Recent polysilane and related copolymer synthesis reactions were reviewed with 140 refs.. The Wurtz-type polymn. of dichloro-, trichloro- or tetrachloro-silanes, so far the most extensively studied, enables access to a large variety of architectures ranging from one- to three-dimensional (3D) topologies, and based on secondary > SiR₂, tertiary RSi(Si)₃ or quaternary Si(Si)₄ silicon units in the polymer backbone. These polysilanes usually present an intrinsic low reactivity, detrimental for fiber processing. Examples are given to illustrate how this reactivity can be increased by secondary substitution reactions, which create reactive entities that can favor further crosslinking reactions. Secondly a novel route involving heterogeneously catalyzed disproportionation of chloromethyldisilanes, developed in our lab., is reviewed which offers a direct access to polysilyne-type 3D architecture constituted by arrangements of fused rings. The Lewis-base catalyzed disproportionation mechanism is discussed and seems to involve donor stabilized silylenes as key intermediates in the polymer formation process. The exptl. results are supported by ab-initio quantum chem. calcns. Silylenes attack the Si sites of higher functionality causing a high regioselectivity for the exclusive formation of branched oligosilanes. The oligomers undergo thermally induced branching and crosslinking reactions leading to poly(chloromethylsilanes). Obviously, there are analogies to the oligomer and polymer formation of the transition-metal complex catalyzed dehydropolymn. of methyldisilanes. Poly(chloromethylsilanes) exhibit a high reactivity due to the presence of Si-Cl bonds. Disproportionation of chloromethyldisilanes in presence of olefins such as styrene provides promising polymer precursors for SiC fibers. Their rheol. properties have been investigated for various styrene contents. The polymer fibers spun from melt are cured under ammonia, and then pyrolyzed to silicon carbide fibers, showing temp. resistance up to 1500 °C.

Synthesis and application of immobilized catalysts for the heterogeneously catalyzed cleavage of the Si-Si bond of chloromethyldisilanes. Richter, Robin; Schulze, Norbert; Roewer, Gerhard; Albrech, Jens. Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. J. Prakt. Chem./Chem.- Ztg. (1997), 339(2), 145-151.
Abstract
Lewis bases like bis(dimethylamide)phosphoryl compds., N-heterocycles, and N,N-dialkylamino-3-propylsilanes bearing alkoxy groups are grafted via siloxane bonds onto silica carriers and characterized. The grafted bis(dimethyl-amide)phosphoryl compds. and N-heterocycles are efficient catalysts for the disproportionation of chloromethyldisilanes into chloromethyloligosilanes and chloromethylsilanes. Grafted N,N-dialkylamino-3-propylsilyl compds. heterogeneously catalyze the Si-Si bond cleavage of the disilanes with HCl at 170  in excellent yields. A mixt. of chloromethylmonosilanes is obtained. This reaction is also performed under pressure.

NMR spectroscopic investigation of the reaction between tetrachlorodimethyldisilane and diethylamine for the synthesis of chloro- and amino-functionalized methyldisilanes. Trommer, K.; Roewer, G.; Brendler, E. Sektion Chemie Physik, Technische Universität Bergakademie Freiberg, Freiberg, Germany. J. Prakt. Chem./Chem.- Ztg. (1997), 339(1), 82-84.
Abstract
The formation of amino(chloro)methyldisilanes from (SiCl₂Me)₂ and Et₂NH was studied by ²⁹Si and ¹³C NMR. Thus, Cl₂Si(Me)Si(NEt₂)MeCl, Et₂NSi(Me)(Cl)Si(NEt₂)MeCl as an inseparable mixt. of diastereoisomers in 3:2 ratio, and Et₂NSi(Me)(Cl)Si(NEt₂)₂Me were prepd.

Base catalyzed hydrogenation of methylbromooligosilanes with trialkylstannanes, identification of the first methylbromohydrogenoligosilanes. Herzog, U.; Roewer, G.. Institute of Inorganic Chemistry, Freiberg University of Mining and Technology, Leipziger Str. 29, D-09596, Freiberg, Germany. J. Organomet. Chem. (1997), 527(1-2), 117-124.
Abstract
The Lewis base catalyzed hydrogenation of methylchlorooligosilanes with trialkylstannanes can also be applied to the hydrogenation of methylbromooligosilanes. In this way methylbromohydrooligosilanes were prepd. for the first time. Methylbromotrisilanes with a SiBrMe middle group (e.g. SiBrMe₂-SiBrMe-SiBrMe₂) are hydrogenated first at this Si atom with formation of a SiHMe group (e.g. SiBrMe₂-SiHMe-SiBrMe₂). Brominated silanes contg. a quaternary Si(Si)₄ unit (e.g. Si(SiBrMe₂)₄) do not react with trialkylstannanes.

Mechanism of the silicide-catalyzed hydrodehalogenation of silicon tetrachloride to trichlorosilane. Walter, Holger; Roewer, Gerhard; Bohmhammel, Klaus. Faculty Chem. and Physics, Freiberg Univ. Mining and Technology, Freiberg, Germany. J. Chem. Soc., Faraday Trans. (1996), 92(22), 4605-4608.
Abstract
A mechanism of transition metal silicide-catalyzed hydrodehalogenation of silicon tetrachloride to trichlorosilane is proposed. The overall reaction includes electron transfer steps from the metal silicide catalyst to adsorbed silicon tetrachloride mols. A silylene species (SiCl₂), which is formed from SiCl₄ and the catalyst surface, is proposed. A hydrogen mol. injects electrons into the solid, whereby hydrogen chloride is generated on the surface. Trichlorosilane results from the oxidative addn. of HCl to chemisorbed SiCl₂.

Immobilization of heavy metals in soils and wastes using sulfides. Pflug, Uwe; Roewer, Gehard; Häfner, Frieder; Wilsnack, Thomas; Wagner, Rolf. (BLZ Geotechnik GmbH, Germany). Ger. Offen. (1996), 9 pp., Patent written in German. Application: DE 95-19513660 19950409.
Abstract
Heavy metals in soils and wastes are mixed with calcium compds. to provide immediate immobilization; the compns. are then reacted with aq. or solid phase sulfides to form compds. which are stable for a long period.

Silicon carbide fibers prepared from chlorine-containing polysilanes. Martin, H.-P.; Richter, R.; Müller, E.; Roewer, G.. Inst. f. Keramische Werkstoffe, TU Bergakademie Freiberg, Germany. Editor(s): Ziegler, Günter. Verbundwerkst. Werkstoffverbunde, [Vortragstexte Tag.] (1996), Meeting Date 1995, 351-354. Publisher: DGM Informationsgesellschaft, Oberursel, Germany
Abstract
A Cl-contg. polysilane was prepd. by a disproportionation reaction of dimethyltetrachlorosilane with trimethyltrichlorodisilane. The SiC fibers were prepd. by spinning the precursor and pyrolysis. The NMR spectra of the fibers show SiC₄ groups to be the predominant nearest neighbor structure. The fibers show no high temp. oxidn. at temps < 1500 °C.

Synthesis of spinnable poly(silanes/-carbosilanes) and their conversion into SiC fibers. Richter, Robin; Roewer, Gerhard; Martin, Hans-Peter; Brendler, Erica; Krämer, Hans; Müller, Eberhard. Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. II, [Muench. Silicontage], 2nd (1996), Meeting Date 1994, 719-723. Publisher: VCH, Weinheim, Germany
Abstract
The heterogeneous catalytic redistribution reaction of methylchlorodisilanes provides spinnable poly(methylchlorosilanes/-carbosilanes). Esp. copolymers like poly(methylchlorosilanes-co-styrenes) are suitable polymers for melt spinning. The high reactivity caused by Si-Cl bonds enables oxygen free curing methods of the melt spun polymer filaments with ammonia. The synthesis is achieved without the employment of highly reactive metals and any solvents. The thus produced SiC fibers exhibit oxygen contents lower than 1 wt. %.

Disproportionation of tetrachlorodimethyldisilane - NMR-spectroscopic identification of the primary products. Brendler, Erica; Leo, Katrin; Thomas, Berthold; Richter, Robin; Roewer, Gerhard; Krämer, Hans. Institut für Analytische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. II, [Muench. Silicontage], 2nd (1996), Meeting Date 1994, 69-73. Publisher: VCH, Weinheim, Germany
Abstract
A review, with 7 refs. The primary oligomers formed during the disproportionation of 1,1,2,2-tetrachlorodimethyldisilane were identified and characterized by ²⁹Si and ¹³C NMR spectroscopy. After initial formation of 1,1,2,3,3-pentachlorotrimethyltrisilane, a branched tetrasilane - tris(dichloromethylsilyl)methylsilane - is formed, demonstrating the preference of branched structures over linear ones. ²⁹Si, ¹³C, and ¹H chem. shifts for both silanes were detd. Knowing the chem. shifts of the oligomers it is possible to assign the signal groups in the polymer spectra to certain structural units and therewith to calc. branching and polymn. degrees for the finally obtained polysilanes.

The catalytic hydrogenation of methylchlorodisilanes with tri-n-butylstannane. Herzog, U.; Roewer, G.; Herzog, K. Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. II, [Muench. Silicontage], 2nd (1996), Meeting Date 1994, 63-68. Publisher: VCH, Weinheim, Germany
Abstract
Bu₃SnH is a valuable reagent for partial conversion of Si-Cl into Si-H functions. Now it is possible to obtain disilanes contg. Me, Cl and H simultaneously by treatment of methylchlorodisilanes with Bu₃SnH in the presence of a catalyst.

Base-catalyzed hydrogenation of chlorosilanes by organotin hydrides. Pätzold, Uwe; Roewer, Gerhard. Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. II, [Muench. Silicontage], 2nd (1996), Meeting Date 1994, 55-62. Publisher: VCH, Weinheim, Germany
Abstract
Bu₃SnH is an effective reagent for partial conversion of Si-Cl into Si-H groups. The hydrogenation mechanism postulates the coordination of the catalyst or the solvent to silicon giving a hypervalent intermediate in the first step, followed by the attack of tributyltin hydride by a single electron transfer or a synchronous hydride transfer. This mechanism implies that the intermediate contg. a hypervalent silicon atom reacts faster than the starting tetracoordinate silane.

Silicides as catalysts for hydrodehalogenation of silicon tetrachloride. Walter, H.; Roewer, G.; Bohmhammel, K.; Vogt, F.; Mörke, W. Institut für Physikalische Chemie, Technische Universität Bergakademie Freiberg, Freiberg, Germany. Editor(s): Auner, Norbert; Weis, Johann. Organosilicon Chem. II, [Muench. Silicontage], 2nd (1996), Meeting Date 1994, 31-39. Publisher: VCH, Weinheim, Germany
Abstract
The catalytic hydrodehalogenation of SiCl₄, from the "Siemens process", to give HSiCl₃ is a fundamental scientific and technol. problem. In this paper, a method to form metal silicides in situ as efficient catalysts will be described, which make it possible to carry out the hydrodehalogenation under mild conditions maintaining the high purity of the products. The generation of all silicide phases in dependence on temp. can be thermodynamically explained by means of equil. calcns. Taking into account our exptl. results for the H₂/SiCl₄/Ni system, a picture of the mechanism of hydrodehalogenation is developed which combines thermodn. and kinetic results.

29Si and ¹³C NMR Investigation of the Polysilane-to-Poly(carbosilane) Conversion of Poly(methylchlorosilanes) Using Cross-Polarization and Inversion Recovery Cross-Polarization Techniques. Babonneau, Florence; Maquet, Jocelyne; Bonhomme, Christian; Richter, Robin; Roewer, Gerhard; Bahloul, Djamila. Chimie de la Matiere Condensee, Université Pierre et Marie Curie/CNRS, Paris, Fr. Chem. Mater. (1996), 8(7), 1415-1428.
Abstract
The polysilane-to-polycarbosilane transformation of polymethylchlorosilane prepd. from based-catalyzed disproportionation of 1,1,2,2-tetrachlorodimethyldisilane has been characterized in detail by ²⁹Si and ¹³C magic angle spinning NMR, using cross-polarization as well as inversion recovery cross-polarization techniques. These techniques allow a clear insight in the protonated environment of a given nucleus, in particular to distinguish between strongly coupled nuclei such as ¹³CH₂ and moderately coupled ones such as ¹³CH₃. For the first time, the IRCP sequence was also used to probe the environment of ²⁹Si nuclei in such systems and proved to be very effective in distinguishing the silane and carbosilane sites. The 180-450 °C temp. range was investigated: the formation of carbosilane units was clearly demonstrated by ¹³C and also ²⁹Si NMR expts. The various ²⁹Si and ¹³C sites were thus identified due to their polarization inversion behavior and quantified. Comparison of these results with a thermogravimetric anal. coupled with mass spectrometry allowed us to propose two different mechanisms for the formation of carbosilane units in such system: at low temp. (T < 180 °C), it is suggested that carbosilane units are formed via condensation reactions between Si-Cl and H-C groups, while at higher temp. (T > 380 °C), the so-called "Kumada rearrangement" occurs.

Silicon carbide fibers derived from chlorine containing polysilanes. Martin, H. -P.; Richter, R.; Müller, E.; Brendler, E.; Roewer, G.. Institute Ceramic Materials, Freiberg University Mining and Technology, Freiberg, Germany. Editor(s): Poursartip, Anoush, Street, Ken. Proc. Int. Conf. Compos. Mater., 10th (1995), 6 307-314. Publisher: Tenth International Conference on Composite Materials Society, Vancouver, Can
Abstract
This paper presents a novel type of SiC fiber manuf. corresponding to the polymer route. New developed chlorine contg. polysilanes are used to spin green fibers. Those fibers are cured under ammonia and temp. treatment to become infusible. After a pyrolysis step around 1000 °C amorphous silicon carbide fibers are obtained. The structure change from polysilane into silicon carbide is obsd. by IR- and NMR- spectroscopy and by x-ray diffraction of the pyrolyzed fibers. The fibers possess a good thermal stability up to at least 1500 °C. Further properties like tensile strength and morphol. are investigated too.

Synthesis and spinning of new polysilanes as SiC fiber precursors. Richter, Robin; Roewer, Gerhard; Brendler, Erica; Krämer, Hans; Martin, Hans-Peter; Müller, Eberhard. Freiberg University Mining and Technology, Freiberg, Germany. Adv. Sci. Technol. (1995), 7(Advanced Structural Fiber Composites), 53-60.
Abstract
Highly reactive chlorine contg. silicon org. polymers are promising precursors for high temp. resistant SiC fibers. The chem. synthesis, spectroscopic investigations and examn. of spinnability of these polysilanes and -carbosilanes are shown in this paper.

Conversion of polycarbosilane fibers into SiC fibers. Martin, Hans-Peter; Brendler, Erica; Müller, Eberhard; Richter, Robin; Roewer, Gerhard. Freiberg University Mining and Technology, Freiberg, Germany. Adv. Sci. Technol. (1995), 7(Advanced Structural Fiber Composites), 45-52.
Abstract
The properties of high temp. resistant silicon carbide fibers, derived from a polymer route, is strongly detd. by the polysilane or polycarbosilane used and the applied curing process. Investigations of a new curing process (using an ammonia curing agent) of chlorine contg. polysilane fibers are shown in this paper. Some resulting properties of the obtained fibers will be addnl. shown.

Preparation of methylchlorohydrotri- and -tetrasilanes via base catalyzed hydrogenation of methylchlorotri- and -tetrasilanes. Herzog, U.; Brendler, E.; Roewer, G.. Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Leipziger Strasse 29, Freiberg/Sa., Germany. J. Organomet. Chem. (1996), 511(1-2), 85-91.
Abstract
The Lewis-base catalyzed hydrogenation of methylchlorodisilanes with trialkylstannanes is also applicable to higher methylchlorooligosilanes without cleavage of the Si-Si bonds. In this way it was possible to prep. methylchlorohydrotri- and -tetrasilanes. Using trisilanes with a >SiClMe middle group the first hydrogenation takes place exclusively at this silicon atom under formation of a >SiHMe group. By hydrogenation with trialkylstannanes it is possible to modify the methylchlorooligosilanes obtained by the disproportionation of methylchlorodisilanes into precursors for polymers. With Me₃SnH as hydrogenation agent the Me₃SnCl formed can easily be removed and re-used.

Catalytic hydrogenation of halosilanes with tributyltin hydride. Pätzold, U.; Roewer, G.; Herzog, U. Freiberg/Sa., Germany. J. Organomet. Chem. (1996), 508(1-2), 147-52.
Abstract
Bu₃SnH is an effective reagent for partial conversion of Si-Cl into Si-H groups. The presented hydrogenation mechanism postulates the coordination of the catalyst (Lewis bases) or the solvent to silicon, giving an intermediate with higher coordinated silicon atom in the first step, followed by the attack of tributyltin hydride by a single electron transfer. This mechanism implies that the intermediate having a hypervalent silicon atom reacts more rapidly than the starting tetracoordinated silane.

Methylchlorooligosilanes as products of the base catalyzed disproportionation of various methylchlorodisilanes. Herzog, U.; Richter, R.; Brendler, E.; Roewer, G.. Institut für Anorganische Chemie Technische Universität Bergakademie Freiberg, Leipziger Str. 29, Freiberg, Germany. J. Organomet. Chem. (1996), 507(1-2), 221-8.
Abstract
The methylchlorodisilanes SiCl₂MeSiCl₂Me (1), SiCl₂MeSiClMe₂ (2) and SiClMe₂SiClMe₂ (3) disproportionate in the presence of a basic catalyst into methylchloromonosilanes and various methylchlorooligosilanes. Oligosilanes involving up to seven Si atoms were identified by ²⁹Si-, ¹³C- ¹H-NMR and GC-MS measurements. Formation of methylchlorooligosilanes is thought to take place via silylene intermediates.

NMR investigation of the polysilane-polycarbosilane transformation of poly(methylcholorsilanes). Babonneau, F.; Richter, R.; Bonhomme, C.; Maquet, J.; Roewer, G.. Chimie Matière Condensée, Université Pierre-et-Marie-Curie, Paris, Fr. J. Chim. Phys. Phys.-Chim. Biol. (1995), 92(10), 1745-8.
Abstract
The pyrolysis of poly(methylchlorosilanes) prepd. by catalytic disproportionation of disilanes leads to the formation of silicon carbide. The first step of the process is a polysilane-to-polycarbosilane transformation, which occurs with the insertion of methylene groups into Si-Si bonds. For the first time, this transformation was studied by ¹³C MAS-NMR, using cross polarization (CP) and Inversion Recovery Cross Polarization (IRCP) techniques.

Polysilane-derived porous SiC preforms for the preparation of SiC-glass composites. Langguth, K.; Boeckle, S.; Müller, E.; Roewer, G.. Institut Keramische Werkstoffe, TU Bergakademie Freiberg, Freiberg, Germany. J. Mater. Sci. (1995), 30(23), 5973-8.
Abstract
Three different types of SiC performs, with open porosities 60-70 %, were prepd. by pyrolysis of polysilanes and polycarbosilanes at 1670 K. Some samples of each type of SiC structure were oxidized in air at 1070 K to promote wetting by the glass melt. Preforms were then applied for gas pressure infiltration with an aluminosilicate glass melt at 1670 K in 3 MPa argon, and the influence of pore-size distribution and surface compn. on infiltration time was investigated. The compn. of the precursors was detd. by chem. anal., and pyrolyzed SiC was analyzed by thermal decompn. The porosity and pore-size distribution of the SiC-preforms were measured on photographs of sample cross-sections. The SiC-glass composites were examd. by light microscopy, SEM and electron scanning microanal.

Hydrodehalogenation of chlorosilanes in the presence of metal silicides: experimental studies of gas and solid phase composition related to thermodynamic calculations. Bohmhammel, K.; Roewer, G.; Walter, H. Inst. Physical Chem. Inst. Inorganic Chem., Faculty Chem. Physics, Freiberg University Mining Technology, Freiberg, Germany. J. Chem. Soc., Faraday Trans. (1995), 91(21), 3879-82.
Abstract

Thermodn. calcns. show, in accordance with exptl. investigations, that transition metals in an H₂-SiCl₄ atmosphere in the temp. range 600-1200 K will react to form metal silicides. With rising temp., stoichiometry will change in the direction of silicides with a higher silicon content. The silicides formed in situ act both as a catalyst and a silicon source for the hydrogenation reaction of SiCl₄ to form silanes. On the basis of the formation enthalpy of the silicides, systematization of silicide formation is possible.

Manufacture of high temperature-resistant low-oxygen and oxygen-free silicon carbide products, especially fibers. Richter, Robin; Martin, Hans-Peter; Roewer, Gerhard; Mueller, Eberhard; Krämer, Hans; Sartori, Peter; Oelschlaeger, Andreas; Habel, Wolfgang; Harnack, Bernhard. (Solvay Deutschland GmbH, Germany). Eur. Pat. Appl. (1995), 12 pp., EP 668254 A2 19950823 Designated States R: BE, DE, FR, GB, IT, NL. Patent written in German. Application: EP 95-101880 19950211. Priority: DE 94-4405603 19940222.
Abstract

The process comprises stabilizing the shape of reactive center-contg. polymeric org. Si compds., e.g., polysilanes, polycarbosilanes, after spinning under inert gas, in the presence of reactive gas or by heat-treatment, and pyrolyzing the fibers under anaerobic conditions in inert atm. at >1000 °C. Methylchlorosilane-styrene copolymer was spun under anaerobic conditions, stabilized in an Ar-NH₃ mixt. at 150 °C for 1 h, and pyrolyzed at 1100 °C for 1 h to give nanocryst. b -SiC fibers having an O content of 0.2%.

Catalytic hydrodehalogenation of halogenated compounds of elements of the fourth Group. Roewer, Gerhard; Pätzold, Uwe; Walter, Holger. (Solvay Deutschland GmbH, Germany). Eur. Pat. Appl. (1995), 7 pp., EP 658359 A2 19950621 Designated States R: AT, BE, CH, DE, ES, FR, GB, IT, LI, NL. Patent written in German. Application: EP 94-119693 19941210. Priority: DE 93-4343169 19931217.
Abstract
Halogen-contg. C or Si compds. are hydrodehalogenated in the presence of H by using a finely dispersed active catalyst system contg. Si and 1 transition metal at 100-1000 °C. Preferably, a Ni silicide catalyst is used. Typically, the procedure is suitable for manuf. of 1-chloro-1,2,2-trifluoroethylene from 1,1,2-trichloro-1,2,2-trifluoroethane (R 113), manuf. of SiHCl₃ from SiCl₄, manuf. of MeHSiCl₂ from MeSiCl₃, or manuf. of Si from SiHCl₃.

Time-resolved luminescence of photographic AgBr_1-xI_x emulsions. Israel, G.; Tauchnitz, H.; Rittmeier, K.; Roewer, G.; Jahr, W. Martin Luther Universität Halle and Filmfabrik, Wolfen, Germany. ICPS' 94: Phys. Chem. Imaging Syst., IS&T's 47th Annu. Conf. (1994), 1 62-4. Publisher: IS&T--The Society for Imaging Science and Technology, Springfield, Va
Abstract
Luminescence decay kinetics was studied of AgBr_1-xI_x microcrystals (0.005 £ x £ 0.05) at 77-180 K. The luminescence lifetime (t ) and luminescence intensity at t = 0 decreased with mol. fraction x of iodide in the AgBr_1-xI_x microcrystals. A model was developed which includes the activation (reemission) of an electron from a trap level into the conduction band as the re-emitting step of the whole radiative recombination. The activated electron may diffuse within the conduction band and may recombine with a trapped hole under emission of radiation. The obsd. multiexponential decay kinetics was a consequence of the distribution of the free enthalpy of activation of the electron.

Organotin chlorides R₃SnCl and R₂SnCl₂ (R = Me, Bu, Ph) can easily be converted into the corresponding hydrides R₃SiH and R₂SiH₂ employing NaH in diethylene glycol dialkyl ethers. Using trialkyltin hydrides like Bu₃SnH in combination with a catalyst (tertiary amines, N-heterocycles, phosphonium or NH₄⁺ salts), Si-Cl bonds in mono- and disilanes are hydrogenated. In the case of disilanes, Si-Si bond cleavage and concurrent hydrogenation can be afforded with strongly nucleophilic catalysts. Partial hydrogenation is also possible. The whole process can be run cyclically.

Catalytic hydrogenation of chlorine containing disilanes with tributylstannane. Herzog, U.; Roewer, G.; Pätzold, U. Institut für Anorganische Chemie, Fakultät für Chemie und Physik der TU Bergakademie Freiberg, Leipziger Str. 29, Freiberg/Sa, Germany. J. Organomet. Chem. (1995), 494(1-2), 143-7.
Abstract
Partial hydrogenation of methylchlorodisilanes and hexachlorodisilane to methylchlorodisilanes and chlorodisilanes resp., is possible by the use of tributylstannane. Electron-pair donators catalyze the hydrogenation reaction. The ²⁹Si NMR chem. shifts and coupling consts. ¹J_SiH of some new methylchlorodisilanes are reported.

SiC/TiC-dispersion composites made from polysilane and titanium. Martin, H. -P.; Habel, D.; Müller, E.; Roewer, G.. Bergakademie Freiberg, Institut für Keramische Werkstoffe, Germany. Editor(s): Leonhardt, G.; Ondracek, G. Verbundwerkst. Werkstoffverbunde, [Vortragstexte Symp. Dtsch. Ges. Materialkd.] (1993), Meeting Date 1992, 91-7. Publisher: DGM Informationsges., Oberursel, Germany
Abstract
SiC/TiC ceramic composites were prepd. by the pyrolysis of methylchloropolysilane or methylchloropolycarbosilane in the presence of powd. Ti. The effects of pyrolysis temp. and Ti content on the wt. loss, O content and structure of pyrolysis product were detd.

Catalyst for the disproportionation of aryl- or alkylhalodisilanes to aryl- or alkylhalomonosilanes and aryl- or alkylhalopolysilanes. Brendler, Erica; Roewer, Gerhard. (Solvay Deutschland GmbH, Germany). Eur. Pat. Appl. (1994), 7 pp., EP 610809 A1 19940817 Designated States R: BE, DE, FR, GB, IT, NL. Patent written in German. Application: EP 94-101625 19940203. Priority: DE 93-4304256 19930212.
Abstract
Nitrogen contg. heterocyclic hydrocarbons were used as disproportionation catalysts for aryl- and alkylhalodisilanes to mono- and polysilanes. The catalyst can be used from the supported material.

Silver(I) complexes of 3-disubstituted 1-methyl-perhydro-1,2,4-triazine-5,6-dithiones. Schmidt, Ute; Sieler, Joachim; Roewer, Gerhard. Fachber. Chem., Tech. Hochsch., Merseburg, Germany. J. Prakt. Chem./Chem.-Ztg. (1994), 336(1), 53-7.
Abstract
Heterocyclic triazine compds. such as 1-methyl-perhydro-1,2,4-triazin-5,6-dithiones react with Ag salts forming complex species [AgL₂]⁺ (L = triazinedithione). In H₂O the complexes are unstable owing to ligand hydrolysis. Stable solid complex [AgL₂]Br (L = 1,3,3-trimethyl-perhydro-1,2,4-triazine-5,6-dithione) can be obtained by the digestion of AgBr-microcrystals with the triazinedithione in MeOH. As shown by x-ray crystal structure anal. the Ag ion in this complex is coordinated trigonal pyramidal by 4 S donor atoms.

Silica-supported phosphine oxide catalyst for the disproportionation of aryl- or alkylhalodisilanes to aryl- or alkylhalomono- and polysilanes. albrecht, Jens; Richter, Robin; Roewer, Gerhard. (Solvay Deutschland BmbH, Ger. Dem. Rep.). Ger. Offen. (1993), 16 pp., DE 4207299 A1 19931125 Patent written in German. Application: DE 92-4207299 19920307.
Abstract
A process for the catalytic disproportionation of aryl- and alkylhalodisilanes to mono- and polysilanes comprises treatment of disilanes, e.g., MeCl₂SiSiCl₂Me, in the gas phase with supported catalyst in which the catalytic component is a bis(dialkylamino)phosphine oxide group which is directly or through an aminoalkylsilyl group (at the siloxy group) bound to the surface of a silica solid phase. The supported catalysts were prepd. and can be represented by the formulas º SiOP(O)(NR₂)₂, [R = C1-4 alkyl, preferably C1-2; º SiO is a siloxy group of the silica surface] and º SiO)₃Si(CH₂)n[NR^b(CH₂)_m]_kNR^aR^c [R^a, R^b = H, alkyl, R^c; R^c = P(=O)(NR₂)₂; k = 0-6; n, m = 2-6, preferably 2-3].

Luminescence of photographic silver bromide iodide microcrystals. Tauchnitz, H.; Roewer, G.; Israel, G.; Rittmeier, K.; Linck, H.; Jahr, W. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Merseburg, Germany. J. Inf. Rec. Mater. (1993), 20(5), 475-96.
Abstract
Ionic cond. (dielec. loss) and luminescence measurements were carried out on cubic I--doped AgBr microcrystals (dg = 0.6 m m). Luminescence measurements under stationary conditions showed that excitation of AgBr_1-xI_x microcrystals (0.005 £ x1- £ 0.05) with l < 470 nm produced a characteristic luminescence band in the emission spectrum. The max. of this band is centered at 550 nm. The time resolved measurements at 77 K demonstrated that the mean lifetime of the luminescence signal decreases if the I- content in the AgBr microcrystals increases. The decay kinetics are multiexponential. Different rate laws were tested. The best fit between the calcd. and exptl. curve was obtained with an exponential distribution in D G¹ (free enthalpy of activation).

Silicon organic polymers as precursor compounds for silicon carbide materials. Richter, Robin; Roewer, Gerhard; Leo, Katrin; Thomas, Berthold. Freiberg, Germany. Freiberg. Forschungsh. A (1993), A832 99-116.
Abstract
A review, of the types and reactions of O-free org. Si polymers as precursors for prepn. of Si carbide materials. Two broad types of Si polymers were considered: (1) polysilanes (with Si-Si bonds) and (2) polycarbosilanes (with Si-C bonds); in addn., copolymers of the 2 broad types were also considered. Topics discussed include growth reactions (e.g., catalytic polymn. of Si-contg. vinyl monomers, dehydrocoupling of organosilanes and disilanes, and catalytic disproportionation of org. disilanes), direct metal condensation, ring-opening polymn., electrochem. condensation, and synthesis of poly(methylchloro)silane-carbosilanes.

Possibilities for preparation of silicon carbide-titanium carbide dispersion materials by using polysilanes. Roewer, G.; Horlbeck, W.; Brendler, E.; Berger, H.; Zott, C.; Martin, H. P. Inst. Anorg. Chem., Bergakad. Freiberg, Germany. Editor(s): Vierkorn-Rudolph, B.; Lillack, D.; Clar, H.-J. Vortr. Poster - Symp. Materialforsch. 1991, 2nd (1991), 3 2165-7. Publisher: Forschungszentrum, Juelich, Germany
Abstract
Fine-cryst. SiC-TiC composites of high bending strength, fracture toughness, and oxidn. resistance were obtained by the pyrolysis of polysilanes at >1000 °C in the presence of Ti compds. followed by sintering at .apprx.1800 °C. The proposed method ensures the formation of SiC-TiC composites with min. O content.

Catalytical conversion of silicon tetrachloride to trichlorosilane: characterization of the nickel silicalite catalyst by ferromagnetic resonance spectroscopy. Mörke, Wolfgang; Vogt, Fritz; Wendlandt, Klaus Peter; Walter, Holger; Roewer, Gerhard. Dep. Chem., Merseburg Tech. Univ., Merseburg, Germany. J. Chem. Soc., Faraday Trans. (1993), 89(7), 1085-7.
Abstract
Formation of nickel silicide in the reaction between Ni supported on silicalite and a gas mixt. (molar ratio, H₂:SiCl₄ = 6:1) was studied. The formation of metal silicides starts at 723 K as detd. by FMR-based Curie temp. measurements. From the signal intensity, it follows that the Si content of the silicides increases with increasing temp. from .apprx.1 at.% at 723 K up to 6 at.% at 865 K. The geff values suggest the presence of two kinds of alloy contg. .apprx.1 at.% Si: one kind, produced at temps. up to 723 K, forms a shell layer at the surface of the Ni metal particle, and the other, generated by decompn. of Si-rich silicides formed at 865 K, is homogeneously alloyed over the whole particle.

Manufacture of trichlorosilane by reducing silicon tetrachloride with hydrogen at atmospheric pressure in the absence of silicon. Roewer, Gerhard; Walter, Holger; Kühn, Petra; Horlbeck, Wolfgang; Vogt, Fritz; Wendlandt, Klaus Peter; Brumme, Johannes. (Chemiewerk Nünchritz GmbH, Germany). Ger. Offen. (1992), 3 pp., DE 4108614 A1 19920924 Patent written in German. Application: DE 91-4108614 19910317.
Abstract
The process comprises passing a mixt. of H₂ and SiCl₄ in mol. ratio 1:2 to 15:1 at 400-800 °C over Si-rich, microporous solid materials having a layered structure. High-purity SiCl₄-satd. H₂ of 15-35 °C was passed in upflow at 9 L/h through a bed of metal- and Al-free zeolites at 750 °C to give a mixt. of SiHCl₃ and SiCl₄. At H₂/SiCl₄ mol. ratio 2, 6, 8, and 12:1, the SiCl₄ conversion ratio to SiHCl₃ was 3.4, 6.3, 12.2, and 16.6 mol.%.

Two-stage process for the reduction of silicon tetrachloride to trichlorosilane. Teichmann, Rolf; Krämer, Hans; Brumme, Johannes; Jäckel, Detlef; Roewer, Gerhard; Horlbeck, Wolfgang; Vogt, Fritz; Wendtlandt, Klaus Peter. (Chemiewerk Nünchritz GmbH, Germany). Ger. Offen. (1992), 3 pp., DE 4041644 A1 19920625 Patent written in German. Application: DE 90-4041644 19901222.
Abstract
The process comprises (a) passing H₂ and SiCl₄ in vol. ratio (0.5-5):1 and at 350-500 °C over a supported hydrogenation catalyst consisting of Group VIII metals and/or a combination of Group IB, IVB, and VIB metals, and (b) passing the resulting gas mixt. over a Si layer. This process is energy-efficient, and the SiHCl₃ is used in the manuf. of high-purity Si. A mixt. consisting of 67 vol.% H₂ and balance SiCl₄ was passed at 440 °C over a SiO₂-supported Ni catalyst to give a gas mixt. consisting of HCl 59.5, H₂ 28, and SiCl₄ 12.4 vol.%, representing a conversion of 54.5%. This gas mixt. was passed at 320 °C over crushed waste Si, and the resulting vapors were condensed at -50 °C for 1 h to give 75 g mixt. consisting of 44 g HSiCl₃ and 31 g SiCl₄.

Method of producing room-light photographic film. Pietsch, Herward; Roewer, Gerhard; Jäkel, Christine; Jaekel, Reinhard; Mauer, Manfred; Bach, Günther. (Filmfabrik Wolfen AG, Germany). Ger. (East) (1992), 6 pp., DD 298969 A5 19920319 Patent written in German. Application: DD 88-321440 19881104.
Abstract
The title method comprises doping the Ag halide crystals with Rh during pptn. at 0.5 * 10^-7 - 10^-3 mol Rh³⁺/mol Ag halide and, then, demineralizing and stabilizing pAg at 7.5-9, and finally surface doping the Ag halide crystals with a dye mixt. contg. Pinacryptol yellow 50-90 and Pinacryptol green 10-50 wt.% at a rate of 0.1-10 g dye mixt./mol Ag halide. The film prepd. from the above emulsion has high room-light stability.

Method to prepare stable photographic silver halide emulsions. Berndt, Eckhart; Heinrich, Burkhard; Leichsenring, Thomas; Berndt, Helga; Roewer, Gerhard. (Filmfabrik Wolfen A.-G., Germany). Ger. (East) (1992), 6 pp., DD 298319 A5 19920213 Patent written in German. Application: DD 87-309911 19871204.
Abstract
Prepn. of a photog. emulsion having Ag/gelatin-ratio >1 by pptn., phys. ripening, removal of sol. salts, and chem. ripening, is characterized that the Ag halide emulsion is thermally treated (2-800) before chem. ripening. The prepn. method is reproducible and economical.

Method for the chemical stabilization of photographic emulsions. Berndt, Eckart; Roewer, Gerhard; Heinrich, Burkhard; Gahler, Siegfried; Kibbel, Hans Ulrich; Dannenberger, Dirk; Roethling, Tilo; Biering, Holger. (VEB Filmfabrik Wolfen, Fotochemisches Kombinat, Ger. Dem. Rep.). Ger. (East) (1990), 5 pp., DD 278422 A1 19900502 Patent written in German. Application: DD 88-323674 19881222.
Abstract
The title method comprises chem. ripening of photog. emulsion in presence of I. The photog. material has improved photog. characteristics.

Method of chemical sensitization of photographic emulsion. Berndt, Eckart; Roewer, Gerhard; Gahler, Siegfried; Heinrich, Burkhard; Kibbel, Ulrich Hans; Bloedorn, Hartmut; Röthling, Tilo; Biering, Holger. (VEB Filmfabrik Wolfen, Fotochemisches Kombinat, Ger. Dem. Rep.). Ger. (East) (1990), 5 pp., DD 278423 A1 19900502 Patent written in German. Application: DD 88-323675 19881222.
Abstract
The title method comprises chem. ripening of photog. emulsion in presence of I. The emulsion has high sensitivity and produces low min. d.

Method of chemical sensitization of photographic emulsion. Berndt, Eckart; Roewer, Gerhard; Heinrich, Burkhard; Gahler, Siegfried; Kibbel, Hans Ulrich; Bloedorn, Hartmut; Röthling, Tilo; Kochmann, Werner. (VEB Filmfabrik Wolfen, Fotochemisches Kombinat, Ger. Dem. Rep.). Ger. (East) (1990), 5 pp., DD 278424 A1 19900502 Patent written in German. Application: DD 88-323676 19881222.
Abstract
The title method comprises chem. ripening of photog. emulsion in presence of I. The emulsion has high sensitivity and produces low min. d.

Method of keeping silver halide photographic emulsion layer clear. Berndt, Eckart; Roewer, Gerhard; Heinrich, Burkhard; Linck, Helmut; Gahler, Siegfried; Dannenberger, Dirk; Röthling, Tilo. (VEB Filmfabrik Wolfen, Fotochemisches Kombinat, Ger. Dem. Rep.). Ger. (East) (1990), 5 pp., DD 278425 A1 19900502 Patent written in German. Application: DD 88-323671 19881222.
Abstract
The title method comprises addn. of I to the photog. emulsion. The photog. emulsion has improved sensitivity and produces reduced min. d. in images.

Method of keeping photographic emulsion clear. Berndt, Eckart; Roewer, Gerhard; Heinrich, Burkhard; Linck, Helmut; Gahler, Siegfried; Kibbel, H. Ullrich; Kochmann, Werner. (VEB Filmfabrik Wolfen, Fotochemisches Kombinat, Ger. Dem. Rep.). Ger. (East) (1990), 5 pp., DD 278426 A1 19900502 Patent written in German. Application: DD 88-323672 19881222.
Abstract
The title method comprises addn. of I to the stabilized emulsion. The emulsion has improved stability and produces low min. d.

Method of keeping silver halide photographic emulsion layer clear. Berndt, Eckart; Roewer, Gerhard; Heinrich, Burkhard; Linck, Helmut; Gahler, Siegfried; Bloedorn, Hartmut; Biering, Holger. (VEB Filmfabrik Wolfen, Fotochemisches Kombinat, Ger. Dem. Rep.). Ger. (East) (1990), 5 pp., DD 278427 A1 19900502 Patent written in German. Application: DD 88-323673 19881222.
Abstract
The title method comprises addn. of I to the stabilized emulsion. The emulsion has improved sensitivity and stability, and produces reduced min. d.

Controlled crystal structure in the silver halide precipitation. Linck, Helmut; Roewer, Gerhard. Sekt. Chem., Bergakad. Freiberg, Freiberg, Ger. Dem. Rep. Chem. Tech. (Leipzig) (1990), 42(10), 433-5.
Abstract
Double jet pptn. of cubic and tabular AgBr_xI_1-x microcrystals having a shell structure is described. The resulting core/shell structure of the crystals is revealed by ESCA and chem. etching combined with electron microscopy.

Characterization of doped photographic silver halide emulsions. Gahler, S.; Roewer, G.. Dir. Forsch. Entwickl., Filmfabrik Wolfen, Wolfen, Ger. Dem. Rep. J. Inf. Rec. Mater. (1990), 18(4), 285-96.
Abstract
Sensitometric effects caused by Ag halide crystal doping with impurity ions is described. Then by means of photo-EMF and dielec. loss measurements the interactions between the charge carriers interstitial AG ion, vacancy, photoelectron and photohole are studied. Relationships between the sensitometric effects and the local distribution of the impurity ions in the crystals are discussed. Examples are given on the doping of Ag halide by metal ions (Rh³⁺, Cd²⁺), sulfide ions, and Ag clusters, generated by pAg variations in the crystal lattice. Such correlations enable one to manipulate the crystals to achieve the desired photog. properties of Ag halide emulsions.

Investigation on sensitization behavior of selected polymethine dyes by ESR spectroscopy, sensitometry and dielectric loss measurements. Siegel, J.; Von Grossmann, J.; Roewer, G.; Besserdich, H.; Rittmeier, K.; Sydow, M.; Stoesser, R. Forschungsstelle Inf. Photochem. Photophys., Akad. Wiss. DDR, Berlin, Ger. Dem. Rep. J. Inf. Rec. Mater. (1990), 18(3), 197-204.
Abstract
The authors had reported in the past that the photog. efficiency of a spectral sensitizer increased with the yield of reduced dye mols., and also when more electrons from these radicals were injected into the silver halide, leading to the formation of developable latent image specks. The 1st process is controlled by the rate of the electron transfer to the light-excited dye. It is proved that the efficiency of the 2nd step depends strongly on the concn. of the interstitial Ag ions. How the concn. of interstitial Ag ions is influenced by the properties of dye and Ag halide is shown. Measurements of dielec. loss were used for this and the results are correlated with EPR-spectroscopic and sensitometric statements.

Preparation of silver halide emulsions for room-light photographic materials. Jäckel, Christine; Pietsch, Herward; Roewer, Gerhard; Jäkel, Reinhard. (VEB Filmfabrik Wolfen, Fotochemisches Kombinat, Ger. Dem. Rep.). Ger. (East) (1989), 5 pp., DD 273906 A1 19891129 Patent written in German. Application: DD 88-317721 19880708.
Abstract
Room-light photog. materials having improved stability are prepd. using Rb-doped AgCl emulsions which are partially converted with 5-35 mol% Br (based upon the total amt. of halogen) after phys. ripening at pH 2.5-5.5.

Signal reversal of photo-emf. pulses on silver halide emulsion layers. Roewer, G.; Rittmeier, K.; Kleinschmidt, B.; Jahr, W. Sekt. Chem., Tech. Hochsh. "Carl Schorlemmer" Leuna-Merseburg, Merseburg, Ger. Dem. Rep. J. Inf. Rec. Mater. (1990), 18(1), 57-60.
Abstract
The transient photovoltage signal of photog. silver halide emulsion coatings shows a characteristic sign change in dependence on the ripening state of the microcrystals. Such anomalous signals seem to be connected with the formation and topog. of deep electron traps on/in the Ag halide crystal.

Ionic conductivity of silver halide emulsions: Measuring the effects of tetraazaindenes. Roewer, G.; Rittmeier, K.; Jahr, W.; Kleinschmidt, B. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer" Leuna-Merseburg, Merseburg, Ger. Dem. Rep. J. Inf. Rec. Mater. (1990), 18(1), 45-56.
Abstract
A microcomputer controlled app. for measuring the dielec. loss of photog. Ag halide emulsions vs. frequency is described. Method is applied to measure the ionic cond. of coatings contg. cubic or tabular AgBr microcrystals (different ripening states) to which tetraazo-indene compds. and phenylmercaptotetrazole resp. were added. Qual. the cond. changes can be explained by a specific interaction of these compds. with the crystal surface influencing the concns. of interstitial Ag ions. They are correlated with results of photocharge decay kinetics and photog. development.

SERS on photographic silver halide emulsions. Kneipp, K.; Jahr, W.; Roewer, G.. Phys. Dep., Humboldt Univ., Berlin, Ger. Dem. Rep. Chem. Phys. Lett. (1989), 163(1), 105-110.
Abstract
SERS investigations on a cyanine dye in photog. Ag halide emulsions with various photog. relevant additives are reported. In addn. to an electromagnetic enhancement due to Ag particles of suitable size and shape a chem. enhancement which is directly connected with the thiosulfate digestion of the emulsion, i.e. the formation of Ag₂S, plays an important role. In photog. emulsions sensitivity centers and SERS active sites are identical. A strong influence of the additives (stabilizers and antifogging agents) on the chem. SERS enhancement was found.

Some effects of zinc and palladium complexes in photographic silver halide systems. Roewer, G.; Gahler, S.; Berndt, E.; Winzer, A. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Leuna, Ger. Dem. Rep. J. Photogr. Sci. (1989), 37(2), 34-7.
Abstract
Au, Zn, and Pd ions interact with gelatins as well as with thioether and NH₃, halide and thiocyanate ions used in photog. Ag halide emulsions. These potential ligands X compete with the binder for the metal ions giving rise to the formation of mixed complexes M(gel)_nX_m(M = Zn, Pd). It was shown that Pd²⁺ and Zn²⁺ are able to stop the phys. ripening process of Ag halide emulsions contg. 1,8-dihydroxy-3,6-dithiaoctane. The 2 ions displace Au ions from the gelatin complex species as shown by radiochem. measurements. The Au(III) thioether complexes undergo a redox-reaction finally forming colloidal Au. The utilization of such chem. relations makes it possible to influence the sensitometric parameters of emulsions, e.g. fog decrease. Zn²⁺ and Pd²⁺ have a synergistic effect when added together.

Metal ions in photographic silver halide emulsion systems. Berndt, E.; Gahler, S.; Roewer, G.. VEB Filmfabrik Wolfen, Wolfen, Ger. Dem. Rep. J. Inf. Rec. Mater. (1988), 16(5), 387-94.
Abstract
Zn ions in photog. silver halide emulsions, which are sensitized by S + Au, cause an improvement of the fog kinetics and shelf storage stability. Combined addn. of Zn and Pd ions give rise to promising synergetic actions in the diminishing of fog.

Metal ions in photographic silver halide systems. Part II. Influence on ripening of silver halides. Roewer, G.; Winzer, A.; Berndt, E.; Gahler, S. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Merseburg, Ger. Dem. Rep. J. Inf. Rec. Mater. (1988), 16(3), 233-43.
Abstract
Zn²⁺ ions added to photog. emulsions are mainly fixed by components of the gelatin-forming complexes. Their concn. in or on the Ag halide crystal depends on the type of the crystal surface (111 > 100), the kind of gelatin, and the concn. of halide ions. It is possible to displace Au ions from the gelatin complexes to the crystal surface by the addn. of Zn²⁺ or Pd²⁺ ions. Phys. ripening of AgBr crystals in solns. contg. 1,8-dihydroxy-3,6-dithiaoctane can be regulated by the addn. of Pd²⁺ and Zn²⁺ ions.

Inert material-containing radiation-sensitive photographic material. Schnabel, Rainer; Schulze, Volkmar; Roewer, Gerhard; Rühl, Ottomar; Reher, Ernst Otto; Gellrich, Peter; Schulz, Hartmut. (Technische Hochschule "Carl Schorlemmer" Leuna-Merseburg, Ger. Dem. Rep.). Ger. (East) (1988), 5 pp., DD 253493 A1 19880120 Patent written in German. Application: DD 86-295377 19861020.
Abstract
A Ag halide photog. material showing improved characteristics, such as swelling value and processing characteristics, under high-temp. development contains in the top layer or the outermost radiation-sensitive hydrophilic colloid layer an inert hydrophobic material, such as hydrophobic SiO₂ or a hydrophobic metal oxide, at 0.1-20 wt.%. A photog. film prepd. with a neg. gelatin-Ag(Br,I) emulsion contg. Aerosil R 972 (hydrophobic SiO₂) was exposed and developed at 38 °C to show improved sensitivity and decreased swelling over a control contg. nonhydrophobic SiO₂.

Silver halide photographic emulsions containing gold complexes. Berndt, Eckhard; Roewer, Gerhard; Berndt, Helga; Friese, Mathias; Hoyer, Eberhard. (VEB Filmfabrik Wolfen, Fotochemisches Kombinat, Ger. Dem. Rep.). Ger. (East) (1987), 7 pp., DD 249106 A1 19870826 Patent written in German. Application: DD 86-290156 19860512.
Abstract
Ag halide photog. emulsion, which can be used for the prodn. of both black-and-whited and color materials, contain a Au complex of the formula M_p[AuL1_mL2_n]X_q (M = H⁺, Na⁺, K⁺, NH₄⁺; L1 = a thio ether, thioamino acid, mercaptoamino acid, amine; L2 = L1, Cl^-, Br^-, I^-, CN^-, SCN^-, S₂O₃^2-; X = Cl^-, Br^-, I^-, AuCl₄, ClO₄^-, NO₃^-; m = 1,2; n = 0-2, p = 0-2; q = 0-2). The emulsions have improved sensitivity and gradation, a low Dmin, and good stability. Thus, to a gelatin-Ag(Br,I) emulsion were added Na₂S₂O₃ and a 1,8-dihydroxy-3,6-dithiooctane-Au complex monochloride, the emulsion chem. ripened, coated on a support, dried, and exposed to show a sensitivity of 37.5, a Dmin of 0.12, and a gradation of 1.8.

Surface and internal image investigations on photographic silver halide emulsions. Method and results. Influence of precipitation condition on the latent image topography. Roewer, G.; Linck, H.; Bernd, E. Tech. Hochsch. "Carl Schorlemmer", Merseburg, Ger. Dem. Rep. J. Inf. Rec. Mater. (1988), 16(1), 3-13.
Abstract
A short review is given on analyzing the methods for the detection of the surface/internal latent image distribution in Ag halide crystals of photog. emulsions. A new developer is described contg. cysteine for the etching of crystals and the development of internal centers. It is applied to investigate the dependence of latent image topog. on grain size, I- distribution in the crystals and Ag digestion during the pptn. The results demonstrate the ability of Ag clusters to act as electron and/or hole traps depending on their size and local site.

Photocharge investigations of chemically-sensitized silver halide evaporated layers. Vaupel, B.; Rittmeier, K.; Roewer, G.. Tech. Univ. Dresden, Dresden, Ger. Dem. Rep. J. Inf. Rec. Mater. (1988), 16(1), 51-6.
Abstract
Photo-EMF measurements of chem. sensitized evapd. AgBr layers may be analyzed according the relation proposed by B. Levy (1983) for emulsion coatings. The ratio of the rate consts. correlate with changes in photog. efficiency during chem. ripening. The 2nd order rate const. is mainly influenced by Au ripening, 1st and 2nd order rate const. by Ir ripening and mainly 1st order rate const. by Pd ripening. Assocd. mechs. are discussed.

Determination of topography of internal latent photographic image. Berndt, Helga; Roewer, Gerhard. (VEB Filmfabrik Wolfen, Fotochemisches Kombinat, Ger. Dem. Rep.). Ger. (East) (1987), 7 pp., DD 244212 A1 19870325 Patent written in German. Application: DD 85-284015 19851210.
Abstract
A process for detg. the topog. of the latent internal image of a Ag halide photog. material involves exposure to a gray wedge, bleaching the latent surface image, development of the latent internal image, fixing, rinsing, drying, and evaluating the characteristic curve in relation to a control with characteristic curves of the total latent image and latent surface image. In prepg. the control, after the latent internal image is bleached, the material is developed in a surface developer contg. a chelating agent for Ag ion whose 1:1 complex has a stability const. >109 at room temp. and whose 1:2 complex has a stability const. >1013 under development conditions with a pH between 7 and 12.

Treatment of silica for controlled hydrophobicity. Schnabel, Rainer; Rühl, Ottomar; Schulze, Volkmar; Roewer, Gerhard; Reher, Ernst Otto; Behrens, Heinz. (Technische Hochschule "Carl Schorlemmer" Leuna-Merseburg, Ger. Dem. Rep.). Ger. (East) (1987), 3 pp., DD 248348 A1 19870805 Patent written in German. Application: DD 86-289437 19860421.
Abstract
The title process, esp. for the modification of pyrogenic SiO₂, consists of treating the SiO₂ with electromagnetic radiation, esp. UV, at 200 nm under O₂ or an inert atm. Aerosil A 200 was treated with O₂(g) and UV radiation for 100 min. The treated material contained OH groups 0.334 mmol/g (1.01 OH groups/nm²) vs. 0.334, 0.557, and 0.672 mmol/g for samples thermally treated before the UV treatment, treated with x-rays, and untreated, resp.

Influencing the gelling kinetics of photographic layers. Schulze, Volkmar; Schnabel, Rainer; Rühl, Ottomar; Vogel, Roland; Reher, Ernst Otto; Roewer, Gerhard; Gellrich, Peter; Protzel, Siegfried. (Technische Hochschule "Carl Schorlemmer" Leuna-Merseburg, Ger. Dem. Rep.). Ger. (East) (1986), 4 pp., DD 241307 A1 19861203 Patent written in German. Application: DD 85-281106 19850927.
Abstract
A process for influencing gelling during cooling of a multilayer photog. emulsion on a support involves the addn. of glass-forming and/or amphoteric metal and nonmetal oxides in different cryst. states as well as salts of the corresponding acids and mixed oxides, esp. SiO₂ dispersions or polymeric silicic or colloidal silicic acid or colloidal SiO₂ or powd. SiO₂, to the single layer or individual layers of the laminate. The process allows control of the gelling and the elimination of defects and faults in the coating process.

Contributions to operating mechanism of potassium palladium chloride (K₂PdCl₄) on the chemical sensitization of silver bromide emulsions with and without gold. Friese, M.; Roewer, G.; Rittmeier, K.; Hoyer, E. Sekt. Chem., Karl-Marx-Univ., Leipzig, Ger. Dem. Rep. J. Inf. Rec. Mater. (1987), 15(3), 155-62.
Abstract
AgBr emulsions consisting of cubic or octahedral crystals (mean diam. 0.5 m m) and inert gelatin were ripened with Au(I) as its thiocyanato complex at 48 °C, giving a max. of speed and a min. of fog (2.7 * 10^-5 mol Au per mol Ag). In the same way samples of emulsions were ripened with the same amt. of Au(I) and different amts. of Pd(II) as K₂PdCl₄ (2 * 10^-6 up to 2 * 10^-4 mol Pd per mol Ag) and in absence of Au(I) with K₂PdCl₄ (5 * 10^-5 up to 5 * 10^-3 mol Pd per mol Ag). The obtained emulsions were examd. sensitometrically (internal and surface image development). The part of Pd which remains in the gelatin was detd. by atom adsorption spectroscopy, and statements are made about the mechanism of latent image formation by DEMBER-expts. On this basis the different hypotheses of chem. sensitization with K₂PdCl₄ are discussed.

Metal ions in photographic silver halide systems. Part II. Interaction of metal ions with the gelatin matrix. Roewer, G.; Gahler, S.; Berndt, B. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Merseburg, Ger. Dem. Rep. J. Inf. Rec. Mater. (1986), 14(6), 433-44.
Abstract

A review with 50 refs. The influence of complex formation in gelatin emulsions with metal ions is shown. The interaction esp. of Zn²⁺ and Cd²⁺ with naturally occurring amino acids is discussed in detail, because it serves as a model to describe the metal ion-peptide bonding.

Metal ions in silver halide photographic systems. Part I. Known action possibilities and photographic effect of foreign ions. Gahler, S.; Roewer, G.; Berndt, E. VEB Filmfabr. Wolfen, Wolfen, Ger. Dem. Rep. J. Inf. Rec. Mater. (1986), 14(6), 427-31.
Abstract
The influence of impurity metallic ions on the Ag halide systems in photog. emulsions is discussed.

Dember effect - investigations on coated layers consisting of photographic silver halide emulsions. Roewer, Gerhard; Rittmeier, K. Tech. Hochsch. "Carl Schorlemmer", Leuna-Merseburg, Ger. Dem. Rep. J. Inf. Rec. Mater. (1986), 14(2), 133-42.
Abstract
Measurements of the Dember effect provide useful information for assessing of sensitometric properties of coated photog. emulsions on several additives and emulsion treatments. Kinetic anal. of transient photocharge signal is possible if a laser flash exposure is employed. A suitable app. and versions of signal anal. are presented. The application of the method described is shown by the obsd. effects of additives and changes of the pAg value during the pptn. of AgBr microcrystals on the photocharge decay.

Stabilizing photographic silver halide emulsions. Gahler, Siegfried; Winzer, Achim; Berndt, Eckhard; Roewer, Gerhard. (VEB Filmfabrik Wolfen, Ger. Dem. Rep.). Ger. (East) (1985), 15 pp., DD 224418 A1 19850703 Patent written in German. Application: DD 84-263445 19840528.
Abstract
Ag halide photog. emulsions can be stabilized during the phys. ripening process, in which thio ethers, thioamino acids, and thiourea derivs. are used as accelerators, by the addn. of uni- or multivalent metal ions at 0.5 * 10^-3-15.0 * 10^-2 mol/mol Ag halide. Thus, to a gelatin-AgBr emulsion was added 1,8-dihydroxy-3,6-dithiooctane 1.5 * 10^-2 mol/mol Ag to accelerate the phys. ripening and for producing AgBr grains with a large av. grain diam. At the end of 120 min phys. ripening, a tetrachloropalladate(II) (I) soln. was added, the emulsion chem. ripened, stabilized, coated on a support, dried, exposed, and developed for 10 min to show a relative sensitivity and a fog d. of 21.5 and 0.36, resp., vs. 17.5 and 0.46, resp., for a I-free control.

Stabilization and clarification of photographic silver halide emulsions. Roewer, Gerhard; Berndt, Eckart; Gahler, Siegfried. (VEB Filmfabrik Wolfen, Ger. Dem. Rep.). Ger. (East) (1984), 9 pp., DD 215409 A1 19841107 Patent written in German. Application: DD 83-250684 19830506.
Abstract
A process for stabilizing and clearing Ag halide photog. emulsions without adversely affecting the sensitivity involves the addn. of a metal compd. of the formula MX_m (M = Zn, Ce, Mn, Co, Ni; X = Cl, Br, SCN, NO₃, NO₂, SO₄, RCO₂ where R = an aliph. or arom. group; m = 1,2) to the emulsion during time intervals between the cutoff of phys. ripening and coating. Thus, a fine-grain gelatin-Ag(Br,Cl) (30 mol% Br^-) was phys. ripened and then 0.027 mmol Au/mol Ag, Na thiosulfate, and MnCl₂ 0.575 mmol/mol Ag added. After phys. ripening for 50-100 min at 45 °C and the addn. of the usual additives, the emulsion was coated on a support, dried, and exposed to show a  of 5.7, a Dmin of 0.18, and no change in sensitivity vs. 5.7 and 0.32, resp., for a MnCl₂-free control.

Chemical sensitization and clarification of photographic silver halide emulsions. Berndt, Eckart; Roewer, Gerhard; Gahler, Siegfried; Winzer, Achim. (VEB Filmfabrik Wolfen, Ger. Dem. Rep.). Ger. (East) (1984), 10 pp., DD 215410 A1 19841107 Patent written in German. Application: DD 83-250686 19830506.
Abstract
A process for the chem. sensitization and fog prevention as well as the stabilization of Ag halide photog. materials involves the addn. of a combination of a Pd or Pt compd. and a divalent metal salt to the emulsion between the phys. ripening and coating. The resultant emulsions have a high sensitivity and a low fog. Thus, to a phys. ripened gelatin-Ag(Br,I) emulsion were added Na thiosulfate, and a Au-thiocyanate complex, K₂[PdCl₄] 0.108, and Zn(NO₃)₂ 0.64 mmol/mol Ag. After the emulsion was chem. ripened for 50-110 min at 52 °C, coating aids were added and the emulsion coated on a support, dried, exposed, and developed to show no change in sensitivity, a  of 0.66, a Dmin of 0.10, and a D20 of 0.44 vs. 0.65, 0.16, and 0.90, resp., for a control contg. neither K₂[PdCl₄] or Zn(NO₃)₂.

Application of modern study methods in photography. Roewer, Gerhard; Winzer, Achim. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Leuna, Ger. Dem. Rep. Wiss. Z. Tech. Hochsch. "Carl Schorlemmer" Leuna-Merseburg (1984), 26(4), 645-63.
Abstract
A review with 27 refrs. in which the use of modern solid-state characterization methods, such as microanal. with x-rays, electron beams, and ion beams, the incorporation of tracers, the measurement of dielec. loss, luminescence, microwave photocond., and Dember effect, in the study and characterization of Ag halide photog. systems is discussed. The examples illustrate that these methods are available for the relating of the sensitometric effect to its mechanistic causes in the realm of chem. and spectral sensitization of Ag halide microcrystals.

Efficiency of the photochemical cobalt-carbon bond cleavage in s -alkyl-cobalt(III)(salen)- and -cobalt(III)(salphen) complexes. Roewer, G.; Kempe, G.; Kolle, B.; Just, R. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Leuna-Merseburg, Ger. Dem. Rep. J. Prakt. Chem. (1982), 324(1), 53-64.
Abstract
The photodealkylation rate of RCoLX (I; R = Me, Et; L = salen, salphen; X = H₂O, py, PPh₃) depends on the ligands, solvent, O₂ concn., and the presence of alkyl radical scavengers. The low quantum yields of anaerobic dealkylation stem from rapid recombination of R.bul. with CoLX; in the presence of O₂ this recombination is prevented and ROOCoLX complexes are formed. Decompn. of these peroxy complexes leads to hydroxyalkyl radicals, which may react with I, resulting in the dependence of the quantum yield on light intensity. The anaerobic photolysis can be accelerated by alkyl radical scavengers, e.g., nitrosodurene.

Determination of small amounts of chloride, bromide and iodide using anion exchange liquid chromatography. Roehse, Werner; Roewer, Gerhard; Boran, Roland; Hellmig, Rolf. VEB Filmfabrik, Wolfen, Ger. Dem. Rep. Z. Chem. (1982), 22(6), 226-7.
Abstract
An anion-exchange chromatog. method with potentiometric detection using ion-selective electrodes is described for detg. small amts. of Cl^-, Br^-, and I^-. KNO₃ soln. was used as the eluent. A combination of Wofatit SL30 and Wofatit AD 41 was used as the stationary phase. Anal. of photog. developing solns. showed that sulfite and org. components do not interfere.

Photolysis of ternary iron(III) complexes with oxalate and phenolate ligands. Roewer, G.; Kempe, G. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer" Leuna-Merseburg, Merseburg, Ger. Dem. Rep. J. Prakt. Chem. (1981), 323(6), 864-8.
Abstract
The overall Fe(II) quantum yields of the photolysis of mixed ligand complexes [Fe(C₂O₄)_3-nL_n]^3- (L = salicylate, sulfosalicylate, or the dianion of catechol, 3,5-disulfocatechol Na salt, tetrachlorocatechol) in aq. soln. within the spectral region 436 nm £ l _irr. £ 546 nm are much smaller than those of the complexes [Fe(C₂O₄)_3-n(H₂O)_2n]^3-2n (n = 0, 1, 2). This indicates that the intramol. photoredox reaction between Fe(III) and the oxalate ligand is not sensitized by the L - Fe(III) charge transfer excitation. Moreover, filter effects through photinactive complexes [FeL₂(H₂O)₂]^- or [FeL(H₂O)₄]⁺ probably give rise to the strong decrease in the quantum yields.

Constitution and redox stability of copper(II) complexes with substituted hydrazines. Kempe, G.; Boegel, M.; Roewer, G.. Sekt. Chem. Tech. Hochsch. Carl Schorlemmer, Leuna-Merseburg, Ger. Dem. Rep. J. Prakt. Chem. (1981), 323(3), 360-6.
Abstract
CuCl₂ was reacted with substituted hydrazines to form chelates of the Cu^IIL₂Cl₂ type (L = RCONHNH₂, RCONHN(C₆H₅)₂, RCONHNHCOR, H₂NNHCO(CH₂)_nCONHNH₂) which were characterized by quant. anal., IR and ESR spectra. The complex polyhedron exhibits the geometry of a tetragonally distorted octahedron of C2_v symmetry. The complexes undergo intramol. redox decompn. in MeCN forming Cu(I) species. The rate consts. increase with decreasing half wave oxidn. potential and decreasing HOMO energy of the hydrazine ligands, resp.

Chemically sensitized photoreduction of chlorocopper(II) complexes. Roewer, Gerhard; Kempe, Gottfried. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Leuna-Merseburg, Ger. Dem. Rep. Z. Chem. (1981), 21(2), 75.
Abstract
The photoredn. of a CuCl₂ (5 * 10^-3 M in DMF and MeCN) soln. in the presence of arom. compds., ketones, quinones, and dyes as sensitizers was studied in order to det. which electronic state in the complex was the starting point for the redox process. For all arom. compds. f [Cu(I)] = 0. For the dyes and heterocycles 0 £ f [Cu(I)] £ 0.36.

Iron(III) complexes with mixed ligands consisting of oxalate and phenolate ligands. Roewer, G.; Kempe, G.; Kretschmer, K.; Wieser, E. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Leuna-Merseburg, Ger. Dem. Rep. J. Prakt. Chem. (1979), 321(1), 75-85.
Abstract
K₃[FeL₃]*nH₂O (H₂L = pyrocatechol, salicylic acid, tetrachloropyrocatechol (I)), K₃[FeQ₂(H₂O)₂]*H₂O (H₃Q = sulfosalicylic acid), and K₃Na₆[Fe(Tir)₃]*5H₂O (Na₂H₂Tir = Tiron) were prepd. and reacted with K₂C₂O4 to give K₃[FeZ₂(C₂O₄)]*nH₂O (H₂Z = H₂L and H₃Q), K₃[Fe(HQ)(C₂O₄)₂]*3H₂O, K₃[FeL(C₂O₄)₂]*3H₂O (H₂L = I), K₃Na₄[Fe(Tir)₂(C₂O₄)]*7H₂O, and K₃Na₂[Fe(Tir)(C2O₄)₂]*5H₂O. Moessbauer and IR spectral data indicate that Fe³⁺ is coordinated both to oxalate and phenolate.

Identification of intermediates in the light-induced cleavage of some s -alkylcobalt(III) complexes using spin trapping experiments. Roewer, G.; Rehorek, D. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Leuna-Merseburg, E. Ger. J. Prakt. Chem. (1978), 320(4), 566-72.
Abstract
During the aerobic photolysis of the complexes [R¹Co(L)Y] [R¹ = Me, Et, Pr; Y = H₂O, py, PPh₃; LH = o-HOC₆H₄CH=NCH₂CH₂N=CHC₆H₄OH-o, 1,2-(o-HOC₆H₄CH=N)₂C₆H₄] and [R²₂Co(bipy)₂]X (R² = Me, Pr, PhCH₂; X = ClO₄^-, I^-) in CHCl₃, alkyl, alkoxy, and hydroxyalkyl radicals were detected by using the technique of spin trapping. Moreover, in the presence of Ph tert-Bu nitrone the photolysis of the Et and Pr complexes [R¹Co(L)Y] produces the spin adduct of H at Ph tert-Bu nitrone. From these results it was concluded that the hydrido complexes [HCo(L)Y] are formed.

ESR studies of the photolysis of -methylcobalt chelates. Roewer, G.; Shagisultanova, G. A.; Woyakin, I. V. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Leuna-Merseburg, Merseburg, E. Ger. J. Prakt. Chem. (1977), 319(6), 1031-5.
Abstract
Anaerobic photolysis (visible light) of I and II (Y = H₂O, Ph₃P, pyridine) in several solvents proceeds by a mechanism involving a homolytic cleavage of the Co-C bond. ESR spectral data for the photolysis products were given.

Fixation of copper(2+) ions in matrixes from polyamide and polyhydrazide acids. Roewer, G.; Slowig, M.; Kempe, G. Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", Leuna-Merseburg, E. Ger. J. Prakt. Chem. (1977), 319(1), 123-32.
Abstract
Pyromellitic dianhydride is polymd. with 4,4'-diaminodiphenyl ether and dihydrazides of oxalic acid, malonic acid, adipic acid, and terephthalic acid to give film-forming polyamide-hydrazide-acids which had reducing and mech. properties that varied with the mole ratio of diamine to dihydrazide. Polymers contg. 0.3 mol dihydrazide and 0.7 mol diamine coordinated cupric ions rather than reducing them. EPR and absorption spectra showed that the ions coordinated with the hydrazide but not with amide groups if the polymer-Cu stoichiometry was >12. Only the terephthalic dihydrazide polymer gave complexing at both amide and hydrazide groups, and both of these complex types exhibited axial geometry.

Photolysis of halocuprate(II) and haloferrate(III) complexes in dipolar aprotic solvents. Roewer, Gerhard; Kempe, Gottfried. Sekt. Verfahrenschem., Tech. Hochsch. "Carl Schorlemmer" Leuna-Merseburg, Merseburg, E. Ger. Wiss. Z. Tech. Hochsch. "Carl Schorlemmer" Leuna-Merseburg (1976), 18(1), 87-96.
Abstract
The quantum yields for the photoredn. in CuCl₂-Me₄N⁺Cl^--solvent, CuBr₂-Me₄N⁺Br^--solvent, and FeCl₃-Me₄N⁺Cl^--DMF systems were studied and obsd. to depend on the concn. of the Cu(II) and Fe(III) halides, the amt. of added halogen ion, the donor no. and the dielec. const. of the solvent, reactivity of the solvent toward the halogen ion, and the wavelength of the radiation. A photolysis mechanism is also given.

Photochemical cleavage of -alkylcobalt(III) chelates. Roewer, Gerhard; Krätzschmar, Carmen; Kempe, Gottfried. Sekt. Verfahrenschem., Tech. Hochsch. "Carl Schorlemmer", Leuna-Merseburg, E. Ger. Z. Chem. (1976), 16(2), 67-8.
Abstract
Quantum yields for the photolyses of cobalt complexes, [MeCo(DMG)₂py], [Co(PhCH₂)₂(dipy)₂]I, [MeCo(salen)chin], and [MeCo(salen)py] were detd. in MeOH and DMF at 436 nm, 491 nm, and 546 nm. Differences in quantum yields were obsd. in MeOH soln. with and without O₂.

Synthesis of ternary copper(II) complexes with aromatic mercapto and amino ligands. Roewer, Gerhard; Kühne, Kerstin; Kempe, Gottfried. Sekt. Verfahrenschem., Tech. Hochsch. "Carl Schorlemmer", Leuna/Merseburg, E. Ger. Z. Chem. (1976), 16(3), 117-18. CODEN: ZECEAL Journal written in German.
Abstract
Cu(II) complexes with arom. mercapto ligands are stabilized by the presence of arom. amine ligands and the following complexes of this type were prepd.: [CuLL']X (L = 1,10-phenanthroline, 2,2'-bipyridine; L' = 3-amino-4-mercapto-6-methylpyridazine; X = ClO₄, Cl) and [CuLL'']ClO₄ (L'' = o-mercaptobenzoic acid). The complexes were characterized by chem. anal., elec. cond., ir spectra, and g-factors. The g-factors indicate a strong Cu-Cu exchange interaction. The ligand L' is bonded to Cu via the amino N and deprotonated S atoms; L'' via the carboxy OH group and the deprotonated S atom. When ethylenediamine replaces the arom. diamines no mixed ligand Cu(II) complexes are formed but rather Cu(en)₂²⁺ and Cu(I) compds. When the aliph. thioglycolic acid is used with the arom. amines, Cu(II) is reduced.

Coordination-active polystyrene-based polymers and their complexes with copper(2+) ions. Roewer, G.; Guskowsky, W.; Conrad, W.; Kempe, G. Sekt. Verfahrenschem., Tech. Hochsch. "Carl Schorlemmer", Leuna-Merseburg, E. Ger. J. Prakt. Chem. (1975), 317(4), 675-81.
Abstract
Lightly crosslinked styrene-divinylbenzene polymer [9003-70-7] was chloromethylated and then treated with benzoic hydrazide [613-94-5] or 1,3,5-triphenylformazan [531-52-2] to give polymers which were substituted with hydrazide or verdazyl groups and complexes with cupric ion. The verdazyl-substituted polymer reduced CuCl₂. The rate of the redn. reaction depended on solvent, with the rate decreasing in the order EtOH, MeCN, DMF, and DMSO, and on the anion of the Cu salt, with Cl salts being reduced more readily than SO₄ or NO₃ salts.

Emf. measurements in molten mixtures of calcium chloride and alkali metal chlorides. Roewer, G.; Emons, H. H. Tech. Hochsch. Chem. "Carl Schorlemmer", Leuna-Merseburg, Ger. Z. Anorg. Allg. Chem. (1969), 370(3-4), 119-27.
Abstract
An app. is described for measuring the emf. of cells of the type Cl₂,C|MCl|CaCl₂-MCl|C,Cl₂ (where M = Li, Na, K, Rb). From the emf., the transport nos. are calcd. of Ca²⁺ and M⁺ relative to Cl^- in molten mixts. of CaCl₂ with LiCl, NaCl, and KCl. The activities of the compds. in the CaCl₂-LiCl and CaCl₂-NaCl s ystems are calcd. by using cryoscopic data from phase diagrams, and the de pendence of the emf. on the activities is reported.

Structure of melts of calcium chloride and alkali metal chlorides. Roewer, G.; Emons, H. H. Tech. Hochsch. Chem. "Carl Schorlemmer", Leuna-Merseburg, Ger. Z. Anorg. Allg. Chem. (1969), 370(3-4), 128-33.
Abstract
The relative mobilities and percentage differences of the cation mobilities were calcd. for molten CaCl₂-MCl systems (M = Li, Na, or K) from the relative cationic transfer nos. A possible structure of the molten mixts. is proposed based on these values. The relative mobilities of the alkali-metal ions are greater than those of the Ca²⁺ ions in the compn. range 0 < x_CaCl2 < 0.9. A preferred coordination of Cl^- ions around the Ca²⁺ ions is assumed and illustrated by a modified hole model to interpret the change of the ionic mobilities as a function of concn.

zusammengestellt von: Uwe Herzog

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Letzte Aktualisierung: 26. Januar 2001