Ligand effects on the properties of Ni(iii) complexes: aerobically-induced aromatic cyanation at room temperature

Abstract

A series of organometallic Ni^II and Ni^III complexes supported by tertadendate ^RN3C⁻ ligands were synthesized and fully characterized using X-ray crystallography, CV, and EPR. Based on the solid state structures, the substituents on the two amine N-donors significantly affect the coordination of the Ni^III centers, while the para substituents of the phenyl C-donor have a reduced effect. This is further supported by electrochemical and spectroscopic measurements that suggest the presence of a less bulky N-substituent of the ^RN3C⁻ ligand leads to a more accessible Ni^III center. These results also suggest that the (^NpN3C)Ni system should be more reactive toward oxidation than the corresponding (^tBuN3C)Ni and (^pOMeN3C)Ni systems. Indeed, aerobic oxidative aromatic cyanation was achieved with the (^NpN3C)Ni system at room temperature.