Radical ions derived from hydrides and methyls of aluminum,silicon and phosphorus: A semi-empirical SCFMO study

Semi-empirical SCFMO calculations were made of the energies, and geometric and electronics structures of a range of radical ions of type MR₃^± and M₂R₆^± where M = Al, Si or P, and R = H or CH₃. In each of the MH₃ radicals, methylation effects an increase in the HMH angle: the structure of Al₂Me₆^?, formed by γ-irradiation of Al₂Me₆, is found to have C_s symmetry and to resemble a weak complex of AlMe₂ and AlMe₄^?. Possible identities for the radical, other than AlH₃^?, formed on γ-irradiation of LiAlH₄ are suggested, and a considerable number of plausible identities are firmly ruled out.