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

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.