Reactivity of Boryl- and Silyl-Substituted Carbenoids toward Alkynes: Insertion and Cycloaddition Chemistry

Three modes of reactivity of phenyl-substituted alkynes toward acyclic tetrelenes are reported, with reaction pathways found to be dependent not only on the nature of the group 14 element but also on the supporting ligand set. Systems featuring Sn-B or Ge-B bonds undergo insertion chemistry, forming borane-appended (vinyl)Sn-II and Ge-II species. With a bis(amido)stannylene, phenylacetylene acts as a profit acid, generating a Sn-II acetylide with a unique bridged structure. Reactivity toward a more strongly reducing Si-II system is dominated by the possibility of accessing Si-IV via [2 + 1] cycloaddition chemistry.