CHEMISTRY OF ALKALI METAL-UNSATURATED HYDROCARBON ADDUCTS. XI. ESR MONITORING OF TRANSIENT RADICAL-ANIONS FROM UNSATURATED ORGANOSILANES

Article abstract of DOI:10.1016/0022-328X(84)85166-9

By the potassium-metal reduction of a series of α,β-unsaturated organosilanes at low temperatures, radical-anionic intermediates were generated.Both the detailed structure of such radical-anions and their chemical transformations were studied by a combination of ESR spectroscopy and chemical characterization.Relatively stable radical-anions were obtained from the methyl(phenyl)silanes, tetraphenylsilane and hexaphenyldisilane, but even these decomposed eventually through cleavage and coupling processes.More labile radical-anions arose from organosilanes of the type, Ph3SiE, where E was chloro, cyclopropyl, substituted biphenyl, vinyl, 1-propenyl and 1-propynyl.In several cases, the transient parent radical-anion could be measured with ESR spectroscopy by working at low temperatures in the presence of HMPT.As an aid to deciding among several possible structural assignments of an ESR spectrum, the actual chemical products obtained from such reductions were scrutinized.The conclusion reached from these studies is that that part of the organosilane molecule bearing the highest free electron spin density in the radical-anion is the site of highest chemical reactivity.Sites of radical-coupling, chemical reduction, isomerization and carbon-silicon bond cleavage can be predicted from such ESR data.