Coordination of an N-heterocyclic phosphenium containing pincer ligand to a Co(CO) 2 fragment allows oxidation to form an unusual N-heterocyclic phosphinito species

Abstract

A tridentate pincer ligand featuring a central N-heterocyclic phosphenium (NHP+) donor has been coordinated to a Co(CO) 2 fragment to generate the Co NHP complex [PPP]Co(CO) 2 (2). The NHP unit adopts an unusual pyramidal geometry with a relatively long Co-P distance, suggesting a stereochemically active nonbonding phosphorus lone pair. Interestingly, treatment of 2 with trimethylamine N-oxide affords [P(P=O) P]Co(CO) 2 (3), in which the Co-bound central phosphorus donor has been oxidized to an unprecedented N-heterocyclic phosphinito species. The bonding and electronic properties of these complexes are discussed in the context of DFT and NBO computational data. © 2011 American Chemical Society.