PHOTOLYSIS OF VINYLTRIS(TRIMETHYLSILYL)SILANE - FORMATION AND OBSERVATION OF A SILENE AND A SILYLENE IN PRIMARY STEPS

Photolysis of cyclohexane solutions containing vinyltris(trimethylsily l)silane produces both the isomeric silene and silylene fragmentation products (trimethylsilyl)vinylsilylene and hexamethyldisilane as prima ry pathways. Both types of transients produced the expected five- and six-membered rings from reactions with dienes as shown by chemical tra pping studies. In reactions with 2-trimethylsiloxybutadiene, the posit ion of the trimethylsiloxy substituent on the pi bond in both silacycl oalkenes, initially allylic to silicon, isomerized at room temperature to the presumably more stable vinylic isomer. Low-temperature UV spec tra as well as chemical trapping studies with triethylsilane, methanol , and a variety of dienes support this mechanistic interpretation.