Ruthenium Complexes Bearing a Tetradentate Hemilabile Ligand: Synthesis, Structure, Hemilabile Feature, and Catalytic Application to C–H Borylation of Unactivated Arenes

Ruthenium complexes bearing a rationally designed tetradentate hemilabile ligand have been developed. The structures of the complexes and the hemilabile feature of the ligand have been disclosed by X-ray crystallography and NMR analyses. Moreover, in a ruthenium-catalyzed C(sp²)–H borylation of unactivated arenes, such a type of complex was found to show superior catalytic reactivity compared to tetradentate or tridentate phosphine ligands, which suggested that the hemilabile feature of the ligand is the key factor in promoting the reaction efficiently.