Harnessing Scorpionate Ligand Equilibria for Modeling Reduced Nickel Superoxide Dismutase Intermediates

Hydrotris(3-phenyl-5-methylpyrazoyl)boratonickel(II) complexes with organoxanthate or dithiocarbamate coligands equilibrate between κ2- and κ3-chelation modes of the scorpionate ligand in solution, connecting N2S2 square-planar and N3S2 pyramidal ligand fields and a spin crossover. The complexes also exhibit quasi-reversible oxidations at low anodic potentials, thus modeling the structure, dynamics, and redox reactivity of the reduced NiSOD active site.