A Mechanistic Study of Thermal Decomposition of 1,1,2,2-Tetramethyldisilane Using Vacuum Ultraviolet Photoionization Time-of-Flight Mass Spectrometry

Thermal decomposition of 1,1,2,2-tetramethyldisilane was performed by flash pyrolysis in a SiC microreactor in the temperature range from 295 to 1340 K, followed by molecular beam sampling and vacuum ultraviolet photoionization mass spectrometry analysis. Density functional theory investigations on the energetics of reactants, intermediates, and products were carried out to support the experimental observations. Energetics for 1,1,2,2-tetramethyldisilane initiation decomposition reactions and important secondary reactions were calculated. Dimethylsilane, dimethylsilyl radicals, dimethylsilylene, trimethylsilane, and tetramethyldisilene were determined as the primary reaction products in the initiation thermal decompositions of 1,1,2,2-tetramethyldisilane. Further decomposition reactions of tetramethyldisilene, such as production of dimethylsilene (m/z = 72) and eventually SiC₃H₄ (m/z = 68) fragments, were examined. Other products from secondary reactions of dimethylsilane and dimethylsilylene such as SiC₂H_2-6 and SiCH_0-4 were also observed. The comprehensive pyrolysis mechanism of 1,1,2,2-tetramethyldisilane was proposed.

Complex of Silylene with Nitrogen: A Combined Matrix-Spectroscopic and Density Functional Theory Study

The quest for a new and productive route to matrix-isolated silylene 1 has led to the observation that the presence of nitrogen is favorable, as under such conditions 1 is stabilized by formation of a donor-acceptor complex 1 x N2. Either matrix photolysis of diazidosilane or pulsed high-vacuum flash pyrolysis of 1,1,1-trimethyldisilane, followed by condensation of the products with nitrogen at 10 K, were applied as synthetic procedures. In a similar manner, complex 1 x CO can be generated. The results are supported by isotopic-labeling studies. The structural elucidation of the new species is based on the comparison of experimental IR and UV/Vis spectra with data from density functional theory calculations.

Reactivity of Ar‘GeGeAr‘ (Ar‘ = C6H3-2,6-Dipp2, Dipp = C6H3-2,6-iPr2) toward Alkynes: Isolation of a Stable Digermacyclobutadiene

The first reactions of the "digermyne" Ar'GeGeAr' (1, Ar' = C6H3-2,6-Dipp2, Dipp = C6H3-2,6-iPr2) with alkynes are reported. 1 reacts with 1 equiv of H5C6CCC6H5 to afford the 1,2-digermacyclobutadiene 2 in high yield, while it reacts with 2 equiv of the less hindered alkyne Me3SiCCH to yield an unexpected bicyclic compound 3. Molecular structures of 2 and 3 were determined by X-ray crystallography. A possible mechanism for the formation of 3 is discussed. The high reactivity of 1, even at room temperature, emphasizes the fundamental differences between the GeGe and CC multiple bonds.