Ligand Redox Noninnocence in Bis(phosphinimine) Diarylamido Pincer Complexes of Nickel

A series of Ni(II) complexes were generated through ligation by a chelating diarylamido ligand bearing diphenylmethylphosphinimine‐based donors in the ortho positions of the aryl groups: HN[2‐(NPPh 2 Me)‐4‐R‐C 6 H 3 ] 2 (RH, Me). This ligand displays both chemical and redox noninnocence, including the generation of a rare, metal‐bound aminyl radical. Several four‐ or five‐coordinate Ni(II) complexes of various geometries were obtained, including chloride, phenoxide, and metallacyclic complexes, the latter of which result from ligand activation. Cyclic voltammetry (CV) of the four‐coordinate complexes showed reversible oxidation events ( E 1/2 = ca. –0.5 V vs. Fc 0/+ ) and the oxidation product of the phenoxide complex was fully characterized. The oxidation was determined to be primarily ligand‐centered, as supported by electron paramagnetic resonance spectroscopy, X‐ray crystallography, and density functional theory (DFT) calculations. More anodic, irreversible oxidation features were also observed for these complexes by CV ( E an = ca. +0.1 V vs. Fc 0/+ ). DFT computations on the second oxidation were consistent with a second ligand‐centered process to generate nitrenium‐like (R 2 N + ) electronic structures. These studies showcase the versatility of this pincer ligand both by stabilizing complexes of varying geometries and coordination numbers and by providing electrons during oxidation.