Reactions of triplet carbonyl compounds and nitroderivatives with silanes

The photoinduced reactions of aromatic and aliphatic carbonyl compounds and nitro derivatives with tetramethylsilane, hexamethyldisilane, and tetrakis(trimethylsilyl)silane were investigated by EPR spectroscopy. The photoreaction of benzophenone with the three silanes was also studied by time-resolved optical techniques. Triplet ketones and quinones reacted with Me'SiSiMe, and with ( Me3Si).,Si by a radical-like displacement mechanism. Homolytic substitution was also observed by reacting photoexcited nitro compounds with the same silanes. The nature of the radical adducts being formed suggests that this reaction is likely to proceed, at least for some of the investigated compounds, via a partial or complete electron transfer (ET). Corroborating evidence for the latter process was sought in polarographic, cyclic voltammetric, and controlled-potential coulometric experiments