Nickel-Borolide Complexes and Their Complex Electronic Structure

Borolides (BC42-) can be considered as dianionic heterocyclic analogues of monoanionic cyclopentadienides. Although both are formally six-p-electron donors, we herein demonstrate that the electronic structure of their corresponding transition metal complexes differs significantly, leading to altered properties. Specifically, the 18-electron sandwich complex Ni(iPr(2)NBC(4)Ph(2))(2) (1) features an similar to 90 degrees angle between the Ni-B-N planes and is best described as a combination of three limiting resonance structures with the major contribution stemming from a formally Ni2+ species bound to two monoanionic radical (BC4 center dot-) ligands. Compound 1 displays two sequential one-electron oxidation events over a small potential range of <0.2 V, which strikingly contrasts the large potential separations between redox partners in the family of metallocenes, and the potential reasons for this unusual observation are discussed.

Automated summary

BC42- and monoanionic cyclopentadienides can be considered analogous, but their electronic structures differ significantly, leading to altered properties in their transition metal complexes. The 18-electron sandwich complex Ni(iPr(2)NBC(4)Ph(2))(2) (1) displays two sequential one-electron oxidation events over a small potential range, contrasting the large potential separations typically seen in metallocenes.