UNIMOLECULAR DISSOCIATION OF TETRAMETHYLSILANE RADICAL-CATION - APPARENT ABSENCE OF AN ION-NEUTRAL COMPLEX INTERMEDIATE

Quantum chemistry calculations and experimental investigations of the unimolecular dissociation step of the molecular radical cation of tetramethylsilane losing a methyl radical to give the m/z 73 trimethyl silyl cation have been carried out. There is an apparent lack of an ion/neutral complex in the minimum energy reaction pathway, where in quaternary carbon compounds there is evidence of such complexes. It is suggested that at interfragment separation distances at which an ion/neutral complex would be expected the electrostatic interactions are ''swamped'' by the strength of the conventional covalent bonding interactions which are an order of magnitude greater than in the quaternary carbon systems at similar separations.