Are carbodiphosphoranes better ligands than N-heterocyclic carbenes for Grubb's catalysts?

摘要

Theoretical investigations suggest that substitution of an N-heterocyclic carbene by a carbodiphosphorane in the Grubb's catalyst for olefln metathesis might lead to enhanced reactivity. Recent experimental and theoretical studies about the bonding situation and reactivity of carbodiphosphoranes C(PR_3)_2 have renewed the interest in this exceptional class of compounds. Carbodiphosphoranes (CDP) are best described in terms of a divalent carbon(0)-atom stabilized by two phosphane groups in contrast to N-heterocyclic carbenes (NHCs) which are divalent carbon(II)-compounds (Scheme 1). A theoretical investigation of the ligand properties of CDPs showed that they are capable of acting as a- and 7t-donor ligands.