- Targeted attachment of functional groups at Ge9 clusters: Via silylation reactions
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Molecules with low-valent Ge atoms are generally synthesized from organohalogen germanes as precursors. The Zintl phase K4Ge9 provides reactive building blocks for a targeted synthesis of germanium-rich molecules. The silylation of Ge9 clusters with chlorosilanes ClSiR2R′, that carry unsaturated olefin groups R′ leads to the introduction of olefinic side chains of variable lengths allowing for further reactions. The compounds K[Ge9{Si(SiMe3)3}2(SiPh2R′)] (R′ = -CHCH2 (1); -(CH2)3CHCH2 (2)) carry one such functionality, whereas K[Ge9(SiPh2R′)3] (3 and 4) offer the possibility for an interconnection of clusters due to three functional groups on the Ge9 core. XPS measurements show that the silylated clusters are much more air-stable than the unsubstituted, bare cluster units.
- Mayer,Schiegerl,Kratky,Günther,F?ssler
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- Iron-catalyzed chlorination of silanes
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A simple and highly efficient iron-catalyzed method for the chlorination of silanes has been developed. By use of 0.5-2% of the Fe(III)-based catalyst FeCl3 or Fe(acac)3 in the presence of 1-1.5 equiv of acetyl chloride as the chlorine donor, a large number of silanes, alkoxysilanes, and silanols were converted to the corresponding chlorosilanes in 50-93% yields. In contrast to earlier reported methods often suffering from expensive catalysts or use of stoichiometric metal salts, hazardous reagents, and reaction conditions, the presently described methodology allows benign reaction conditions and simple workup while using only catalytic amounts of a readily available and economically viable iron catalyst.
- Savela, Risto,Zawartka, Wojciech,Leino, Reko
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experimental part
p. 3199 - 3206
(2012/06/04)
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- Vinyl dichlorosilane and vinyl dibromosilane (H2C=CH-SiHX2, X = Cl, Br): Conformational structure and vibrational properties determined by gas-phase electron diffraction, ab initio molecular orbital calculations, and variable-temperature Raman spectroscopy
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The molecular structures, conformations, vibrational spectra, and torsional potentials of vinyl dichlorosilane (VDC) H2C=CH-SiHCl2, and vinyl dibromosilane (VDB) H2C=CH-SiHBr2, have been studied using gas-phase electron diffraction (GED) data at 23-25°C and variable-temperature Raman spectroscopy, together with ab initio molecular orbital calculations. The GED data were handled by a dynamic theoretical model using a cosine Fourier potential function in describing the torsional coordinate. According to the GED refinements, these molecules exist in the gas phase at room temperature as a mixture of two minimum energy conformers, syn (torsional angle φ(CCSiH) = 0°) and gauche (torsional angle φ(CCSiH) ? 120°). Relevant structural parameters for syn-VDC are as follows: Bond lengths (r(g)): r(Si-C) = 1.847(5) A?, r(Si-Cl) = 2.042(2) A?, r(C=C) = 1.357(7) A?. Bond angles (angle(α)): angle CSiCl = 110.3(6)°, angle CCSi = 121.8°(calc.). Relevant structural parameters for syn-VDB are as follows: bond lengths (r(g)): r(Si-C)= 1.827(9) A?, r(Si-Br) = 2.206(2) A?, r(C=C) = 1.366(10) A?. Bond angles (angle α): angle CSiBr = 110.1(8)°, angle CCSi=121.7°(calc.). Uncertainties are given as 2σ (σ includes estimates of uncertainties in voltage/height measurements and correlation in the experimental data). From the variable-temperature Raman investigation in the liquid phase, the energy differences are: VDC, ΔE°(S-G) = + 0.11 ± 0.06 kcal mol-1; VDB, ΔE°(S-G) = + 0.23 ± 0.07 kcal mol-1. The Raman energies are average values obtained from two separate line doublets for each molecule, and they have been used in the GED least-squares refinements as valuable constraints. (C) 2000 Elsevier Science B.V.
- Johansen,Hagen,Hassler,Richardson,P?tzold,Stolevik
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p. 257 - 279
(2007/10/03)
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