Photolysis of (trimethylsilyl)-, bis(trimethylsilyl)- and pentamethyldisilanylketene in hydrocarbon solution in the presence of aliphatic alcohols affords alkoxysilanes from trapping of silene reactive intermediates. The silenes (1,1,2-trimethylsilene, 1,1,2-trimethyl-2-(trimethylsilyl)silene, and 1,1-dimelhyl-2-trimethylsirene) can be viewed as the products of [1,2]-methyl or -trimethylsilyl migration in the silyl carbene formed by photodecarbonylation of the ketene, although a competing direct excited-state pathway cannot be ruled out. Far-UV (193 nm) laser flash photolysis of the compounds in hydrocarbon solution affords transients which are formed during the similar to 20 ns laser pulse:and are assignable to the silenes on the basis of their UV absorption spectra and reactivity toward alcohols. 1,1,2-Trimethylsilene has also been generated by laser flash photolysis of (trimethylsilyl)diazomethane and -diazirine in hexane and acetonitrile solution, and. its spectrum and rate constants for; reaction with MeOH, MeOD, and t-BuOH have been determined. Those in hexane agree with those obtained using the corresponding ketene as the precursor. The rate constants for addition of ROH to these and three: other 2-substituted 1,1-dimethylsilenes correlate with the resonance substituent parameter sigma(R)degrees, affording rho(R) values of +8.0 +/-2.2 and +6.5 +/- 2.6 for MeOH and t-BuOH, respectively. This allows the conclusion that the reactivity of simple silenes toward nucleophiles is enhanced by resonance electron-acceptor substituents at carbon. To probe for the possible intermediacy of (trimethylsilyl)carbene in the formation of 1,2,2-trimethylsilene from these compounds, flash photolysis experiments with (trimethylsilyl)ketene, -diazomethane, arid -diazirine in the presence of pyridine have been carried out,Absorptions assignable to the carbene-pyridine ylide were observed from the ketene and the diazirine, allowing an estimate of between 0.1 and 0.4 ns for the lifetime of singlet(trimethylsilyl)carbene-in hydrocarbon solvents at room temperature.