End Group Analysis Accounts for the Low Molecular Weight Observed in the 1,3-Divinyltetramethyldisiloxane−Pt Complex Catalyzed Hydrosilylation Copolymerization of α,ω-Dienes and 1,3-Dihydridotetramethyldisiloxane

The 1,3-divinyltetramethyldisiloxane−Pt complex (Karstedt catalyst) facilitates copolymerization of α,ω-dienes, such as 1,7-octadiene or 1,5-hexadiene, with 1,3-dihydridotetramethyldisiloxane. Spectroscopic analysis of the copolymers indicates the presence dimethylsiloxy and either 2-octenyl or 2-hexenyl end groups. Apparently, the catalyst not only facilitates the hydrosilylation reaction of 1,3-dihydridotetramethyldisiloxane with terminal C−C double bonds but also catalyzes the isomerization of terminal alkenes to internal alkenes, which are not reactive.