The mechanism of silicon-fluorine and silicon-carbon bond cleavage in organofluorosilanes and -silicates is analyzed with the aid of molecular orbital calculations. The optimized geometries of reactants and intermediates are calculated, and these calculations support the view that cleavage of Si-F bonds occurs by way of fluorine-bridged Si-F-Si intermediates. Cleavage of a Si-C bond in PhSiF(3) takes place in the presence of fluoride ion and oxidizing agents, and the calculations are in agreement with the formation of PhSiF(4)(-) and PhSiF(5)(2-), followed by oxidation to a radical anion PhSiF(5)(-) The latter species, however, is predicted to decompose rapidly to give anionic SiF5-, and phenyl radicals. These calculations and the proposed mechanisms of bond cleavage are in agreement with experimental data, where available.