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Herein a convenient synthetic method to obtain 2,2,3,3-tetrasilyltetrasilane 3 and 2,2,3,3,4,4-hexasilylpentasilane 4 on a multigram scale is presented. Proton-coupled 29Si NMR spectroscopy and single-crystal X-ray crystallography enabled unequivocal structural assignment. Owing to their unique properties, which are reflected in their nonpyrophoric character on contact with air and their enhanced light absorption above 250 nm, 3 and 4 are valuable precursors for liquid-phase deposition (LPD) and the processing of thin silicon films. Amorphous silicon (a-Si:H) films of excellent quality were deposited starting from 3 and characterized by conductivity measurements, ellipsometry, optical microscopy, and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Herein a convenient synthetic method to obtain 2,2,3,3-tetrasilyltetrasilane 3 and 2,2,3,3,4,4-hexasilylpentasilane 4 on a multigram scale is presented. Proton-coupled 29Si NMR spectroscopy and single-crystal X-ray crystallography enabled unequivocal structural assignment. Owing to their unique properties, which are reflected in their nonpyrophoric character on contact with air and their enhanced light absorption above 250 nm, 3 and 4 are valuable precursors for liquid-phase deposition (LPD) and the processing of thin silicon films. Amorphous silicon (a-Si:H) films of excellent quality were deposited starting from 3 and characterized by conductivity measurements, ellipsometry, optical microscopy, and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Herein, we report on the first sila-aldol reaction, which emphasizes the tight connection between silicon and carbon chemistry. This novel synthetic method provides straightforward access to 2-oxahexasilabicyclo[3.2.1]octan-8-ide, a structurally complex silicon framework, in quantitative yield. Its structure was confirmed by NMR spectroscopy and X-ray crystallography, and it displays a distinctive charge-transfer transition. The complete mechanism of this highly selective rearrangement cascade is outlined and supported by density functional theory (DFT) calculations, which highlight the thermodynamic driving force and the low activation barriers of this powerful silicon-carbon bond-forming strategy. [ABSTRACT FROM AUTHOR]

Herein, we report on the first sila-aldol reaction, which emphasizes the tight connection between silicon and carbon chemistry. This novel synthetic method provides straightforward access to 2-oxahexasilabicyclo[3.2.1]octan-8-ide, a structurally complex silicon framework, in quantitative yield. Its structure was confirmed by NMR spectroscopy and X-ray crystallography, and it displays a distinctive charge-transfer transition. The complete mechanism of this highly selective rearrangement cascade is outlined and supported by density functional theory (DFT) calculations, which highlight the thermodynamic driving force and the low activation barriers of this powerful silicon-carbon bond-forming strategy. [ABSTRACT FROM AUTHOR]

In this contribution a convenient synthetic method to obtain tetraacylgermanes Ge[C(O)R]4 (R=mesityl ( 1 a), phenyl ( 1 b)), a previously unknown class of highly efficient Ge-based photoinitiators, is described. Tetraacylgermanes are easily accessible via a one-pot synthetic protocol in >85 % yield, as confirmed by NMR spectroscopy, mass spectrometry, and X-ray crystallography. The efficiency of 1 a, b as photoinitiators is demonstrated in photobleaching (UV/Vis), time-resolved EPR (CIDEP), and NMR/CIDNP investigations as well as by photo-DSC studies. Remarkably, the tetraacylgermanes exceed the performance of currently known long-wavelength visible-light photoinitiators for free-radical polymerization [ABSTRACT FROM AUTHOR]

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In the present study, we examined photochemical transformations of acylcyclohexasilanes (Me3Si)2Si6Me12(Me3Si)COR (compounds 1) with aromatic substituents attached to the carbonyl C atom. When photolyzed at wavelengths above 300 nm in hydrocarbon solvents, 1a- c ( 1a: R = o-Tol; 1b: R = 2,3-Me2C6H3; 1c: R = 2,4-Me2C6H3) afforded the previously unknown eight-membered heterocyclopolysilanes 3a- c, which feature endocyclic Si=C double bonds with remarkable selectivity. If two ortho-alkyl groups are present at the aromatic ring (compounds 1d- f), the primary products of type 3 ( 3d: R = Mes; 3e: R = 1,6-Me2C6H3; 3f: R = 2,4,6- iPr3C6H2) are photochemically unstable and undergo intramolecular C-H-bond addition reactions of a ortho-CH3 group to the Si=C double bond, which leads to the formation of spirobenzocyclobutenes. When photolysis was performed in the presence of methanol, the expected 1,2-addition products (compounds 4) of the Si=C double bond were obtained quantitatively in all cases. 4a (R = o-Tol) and 4b (R = Mes) were isolated by crystallization from acetone and fully characterized spectroscopically and by single-crystal X-ray diffraction analysis. Interestingly 4b was obtained as an isomeric mixture arising from syn and anti addition of methanol to the endocyclic Si=C bond, whereas the syn addition was observed exclusively in the case of 4a. [ABSTRACT FROM AUTHOR]

Acylcyclohexasilanes are interesting starting materials for the formation of cyclic silenes. Employing standard cyclopolysilane synthetic procedures, nine previously unknown acylcyclohexasilanes were synthesized and characterized by NMR, and UV-Vis spectroscopy and X-ray crystallography to elucidate substituent influences of the R-group attached to the carbonyl C-atom. [ABSTRACT FROM AUTHOR]