Insertion of CO2, Isocyanates, and Acetonitrile into the P-Si Bond of a Silyl-Substituted N‑Heterocyclic Carbene Phosphinidene.

This work investigates the reactivity of IDippP-SiMe3 (IDipp = 1,3-bis-(2,6-diisopropylphenyl)-imidazolin-2-ylidene) toward CO2, Ph-NCO, and Me-CN. Whereas carbon dioxide and phenyl isocyanate readily insert into the polarized P-Si bond, the activation of acetonitrile only proceeds via a frustrated Lewis pair (FLP) pathway in the presence of group 13 halides. Nitrile insertion in the presence of aluminum halides affords both an N-heterocyclic carbene phosphinidene (NHCP)-substituted imine and a phosphaalkene, with the product ratio depending on the choice of Lewis acid. In contrast, the addition of BCl2 m Ter ( m Ter = 2,6-(2,4,6-methyl-C6H2)-C6H3) selectively affords an NHCP-substituted imine via dehalosilylation.