THE ELECTRONIC STRUCTURES OF P(III) COMPOUNDS WITH P[sbnd]C BONDS

Abstract

A valence theory investigation of substituted phosphines with carbon-containing substituents has been carried out. Ab initio molecular orbital calculations at minimal and extended basis set levels were used to determine substituent effects of alkyl and substituted alkyl radicals, unsaturated groups (CN. C₂H, vinyl, allyl), and phenyl and substituted phenyl groups. The interaction of PH₂, PH⁺ ₃ and PH⁻ groups with alkyl and aryl groups is analyzed and compared with the behaviour of the corresponding nitrogen-containing species. Hyperconjugative interactions are very small and pπ-pπ and dπ-pπ conjugation make only a marginal contribution to the P[sbnd]C interaction in PH₂ · C₆H₅. Conjugation is much more important in the charged species PH₃ · C₆H₅ ⁺ and PH · C₆H₅ ⁻. d-Orbitals contribute to the electron distributions of these compounds in a marginal valence role only.