The photolysis of 1,1-dimethylsilacyclobutane in the gas phase

The gas phase photolysis of 1,1-dimethylsilacyclobutane (DMSCB) has been carried out at wavelenghts 185 nm <λ < 210 nm. The major products of the photodissociation are ethylene and 1,1,3,3-tetramethyl-1,3-disilacyclobutane (TMDSCB). The relative quantum yield Φ(C₂H₄)/Φ(TMDSCB) = 8.0 ± 0.5 in neat DMSCB is independent of the initial pressure but decreases to a limiting value of ca. 4.5 in the presence of H₂. The silicon mass deficit is accounted for, qualitatively, by the production of an involatile polymeric material, of approximate composition -(Me₂SiCH₂)_x-, on photolysis. Under these cnditions, Me₂SiCH₂ undergoes an oligomerisation reaction in addition to the established homegenoous dimerisation reaction to form TMDSCB.