Ligand Centered Reactivity of a Transition Metal Bound Geometrically Constrained Phosphine

Abstract

The electronic properties, coordination chemistry and reactivity of metal complexes of a planar (C2v symmetric) acridane‐derived geometrically constrained phosphine, P(NNN), are described. On complexation to metal centers, the phosphine was found to adopt a distorted trigonal pyramidal structure with a high barrier to pyramidal inversion (22.3 kcal/mol at 298 K for Au[P(NNN)]Cl). Spectroscopic data and theoretical calculations carried out at the density functional level of theory indicate that P(NNN) is a moderate σ‐donor, with significant π‐acceptor properties. Despite the distortion undergone by the phosphorus atom on coordination to metal centers, the P(NNN) ligand retains its ability to react with small molecule substrates with polar E–H bonds (MeOH, NH2Ph, NH3). It does so in a concerted fashion across one of the P–N bonds, and reversibly in the case of amine substrates. This cooperative bond activation chemistry may ultimately prove beneficial in catalysis.