Oxidative Addition of Dihydrogen, Boron Compounds, and Aryl Halides to a Cobalt(I) Cation Supported by a Strong-Field Pincer Ligand.

Cationic cobalt(I) dinitrogen complexes with a strong-field tridentate pincer ligand were prepared and the oxidative addition of polar and non-polar bonds was studied. Addition of H to [(PNP)Co(N)] (PNP = 2,6-bis((diisopropylphosphaneyl)methyl)pyridine) in THF- resulted in rapid oxidative addition and formation of the -Co(III) dihydride complex, -[(PNP)Co(H)L] where L = THF or N. The addition of H was reversible as evidenced by the dynamics observed by variable temperature H NMR spectroscopy and the regeneration of [(PNP)Co(N)] upon exposure to dinitrogen. In contrast, addition of HBPin, (Pin = pinacolato) BPin and aryl halides resulted in the formation of net one-electron oxidation products: cationic Co(II)-boryl and Co(II)-halide/aryl complexes, respectively. All products were structurally characterized by X-ray crystallography and the electronic structures were determined by a combination of magnetic moment measurements, EPR spectroscopy and DFT calculations. Monitoring the addition of HBPin to [(PNP)Co(N)] provided evidence for a transient Co(III) oxidative addition product that likely undergoes comproportionation with the cobalt(I) starting material to generate the observed Co(II) products.