Two-electron reactivity of [N2O2red]ZrL3 (1a, N2O2(red) = N,N'-bis(3,5-di-tert-butyl-2-phenoxy)-1,2-phenylenediamide, L = THF) was explored with halogens and 1,2-diphenylhydrazine. Despite a formal d0 zirconium(IV) metal center, halogen oxidative addition occurred to form [N2O2(ox)]ZrCl2(THF) (2) with two-electron oxidation of the ligand. This ligand redox activity allows catalytic reactivity with 1,2-diphenylhydrazine resulting in disproportionation to form aniline and azobenzene via a putative zirconium-imide intermediate.

ML n (M = Ti, L = py, n = 2; M = Zr, Hf, L = thf, n = 3). The redox-active ligand occupies four equatorial coordination sites in these complexes. In the case of the zirconium and hafnium complexes, two axial solvent molecules coordinate to the metal center with a third solvent molecule coordinating in the equatorial plane. In the case of the smaller tita-