SILICON-FLUORINE AND SILICON-CARBON BOND-CLEAVAGE IN ORGANOFLUOROSILICATES - A MOLECULAR-ORBITAL STUDY

The mechanism of silicon-fluorine and silicon-carbon bond cleavage in organofluorosilanes and -silicates is analyzed with the aid of molecul ar orbital calculations. The optimized geometries of reactants and int ermediates are calculated, and these calculations support the view tha t cleavage of Si-F bonds occurs by way of fluorine-bridged Si-F-Si int ermediates. Cleavage of a Si-C bond in PhSiF(3) takes place in the pre sence of fluoride ion and oxidizing agents, and the calculations are i n agreement with the formation of PhSiF(4)(-) and PhSiF(5)(2-), follow ed by oxidation to a radical anion PhSiF(5)(-) The latter species, how ever, is predicted to decompose rapidly to give anionic SiF5-, and phe nyl radicals. These calculations and the proposed mechanisms of bond c leavage are in agreement with experimental data, where available.