A Structurally Characterized Cu III Complex Supported by a Bis(anilido) Ligand and Its Oxidative Catalytic Activity

Three copper(II) complexes of the ( R , R )‐ N , N ′‐bis(3,5‐di‐ tert ‐butyl‐2‐aminobenzylidene)‐1,2‐diaminocyclohexane ligand, namely [Cu( N L)] , [Cu( N LH)] + and [Cu( N LH 2 )] 2+ , were prepared and structurally characterized. In [Cu( N LH 2 )] 2+ the copper ion lies in an octahedral geometry with the aniline groups coordinated in equatorial positions. In [Cu( N L)] the anilines are deprotonated (anilido moieties) and coordinated to an almost square‐planar metal ion. Complex [Cu( N L)] displays two oxidation waves at E 1/2 ox, 1 =−0.14 V and E 1/2 ox, 2 =0.36 V vs. Fc + /Fc in CH 2 Cl 2 . Complex [Cu( N LH 2 )] 2+ displays an irreversible oxidation wave at high potential (1.21 V), but shows a readily accessible and reversible metal‐centered reduction at E 1/2 red =−0.67 V (Cu II /Cu I redox couple). Oxidation of [Cu( N L)] by AgSbF 6 produces [Cu( N L)] (SbF 6 ), which was isolated as single crystals. X‐ray structure analysis discloses a contraction of the coordination sphere by 0.05 Å upon oxidation, supporting a metal‐centered process. Complex [Cu( N L)] (SbF 6 ) displays an intense NIR band at 1260 nm corresponding to an anilido‐to‐copper(III) charge transfer transition. This compound slowly evolves in CH 2 Cl 2 solution towards [Cu( N LH)] (SbF 6 ), which is a copper(II) complex comprised of both anilido and aniline groups coordinated to the metal center. The copper(III) complex [Cu( N L)] (SbF 6 ) is an efficient catalyst for benzyl alcohol oxidation, with 236 TON in 24 h at 298 K, without additives other than oxygen and a base.