C(sp3)–H Amination with an Ammonia-Derived Copper(III) Amide

Metal-ammine (NH3) and metal-amide (NH2) species are common intermediates in ammonia oxidation, typically designed with weak N-H bonds to facilitate the sequential breakage of N-H bonds. Since the σ-bonding interaction between a metal center and an NH3 ligand weakens the N-H bonds, M-NH3 complexes with high N-H bond dissociation free energy (BDFE) are rare. However, we are particularly interested in M-NH3 complexes with high BDFEN-H for their potential in the conversion of C(sp3)-H bonds to C(sp3)-NH2 bonds. Herein, we report the synthesis and characterization of copper(II) and formal copper(III) NH3 and NH2 complexes derived from ammonia (NH3). The N-H bond dissociation free energy (BDFE) of the copper(II) ammine complex (LCuIINH3, L = [N,N'-bis(2,6-diisopropylphenyl)-2,6-pyridine-dicarboxamido]2-) was measured to be 92.8(1.5) kcal/mol, the highest N-H bond strength reported for an M-NH3 species. The copper(III) amide congener (LCuIIINH2) is reactive toward C(sp3)-H functionalization, efficiently mediating the C(sp3)-H activation and C(sp3)-N bond formation, producing a range of functionalized hydrocarbon products, including nitriles, ketones, and primary amines.