The reactions of methyl radicals with silane, disilane ,phenylsilane, and their Si-deuterated analogs, which proceed via H or D abstraction, have been studied by 0. P. Sfruusz, E. Jakubowski, H . S. Sandhu, and H. E. Gunning. The methyl radicals were produced by photolysis of azomethane and the product distributions determined by mass spectrometry and gas chromatography. Silanes are more reactive than hydrocarbons; the activation energies of the reactions are lower, while the pre-exponential factors are equal. The reactions CH;+ CH4 = CH4 + CH;
(1) and CH; + SiH4 = SiH; + CH4
(2) are compared as an example: the activation energies are 14.65 kcal mole-1 for eq. ( 1) and 6.99 kcal mole-1 for eq. ( 2); the logarithms ofthepre-exponential factors are 11.83 cm3 mole-1 s-1 for eq. ( 1) and 11.80 cm3 mole-1 s-1 for eq. ( 2). / J. chem. Physics 51, 552 (1960) /-Hz. [Rd 102 IE] Trimethyltin isothiocyanate is reported by R . A. Forder and G. M. Sheldrick to consist of zig-zag chains containing linear S . . . Sn-N-C-S units arranged along the z axis of the orthorhombic unit cell (a = 13.20, b = 10.28, c = 12.01, all ~0 . 0 1 A; Z = 8; dcalc. = 1.82 g/cm3), the bond angle at the S atom being 97 rt 2O. The C3Sn unit is almost planar with d SnC = 2.13 f 0.03 A. Theinteratomic distances are S . . . Sn 3.13 f 0.02, SnN 2.15 f 0.06, NC 1.15 f 0.07, and CS 1.64 f 0.07 A; the bond lengths in the NCS group lie between those in HN=C=S and CH3S-C =N and thus suggest resonance of the kind 9 d e e =S . . . Sn-N=C=S.. . Sn-N= ++ -S-Sn-N=C-S-Sn-NF which requires no contributions from @+d), bonding to explain the stereochemistry. / Chem. Commun. 1969, 1125 / -HB.