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 nonpolar bonds
was studied. Addition of H2 to [(iPrPNP)­Co­(N2)]+ (iPrPNP = 2,6-bis­((diisopropylphosphaneyl)­methyl)­pyridine)
in deuterated tetrahydrofuran (THF) resulted in rapid oxidative addition
and formation of the cis-Co­(III) dihydride complex, cis-[(iPrPNP)­Co­(H)2L]+,
where L = THF or N2. The addition of H2 was
reversible as evidenced by the dynamics observed by variable-temperature 1H NMR spectroscopy and the regeneration of [(iPrPNP)­Co­(N2)]+ upon exposure to dinitrogen. In
contrast, addition of HBPin (Pin = pinacolato), B2Pin2, 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, electron paramagnetic
resonance spectroscopy, and density functional theory calculations.
Monitoring the addition of HBPin to [(iPrPNP)­Co­(N2)]+ 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.