Syntheses, structures and electrochemical properties of homoleptic ruthenium(III) and osmium(III) complexes bearing two tris(carbene)borate ligands

Six-coordinate homoleptic ruthenium(III) and osmium(III) N-heterocyclic carbene complexes [PhB(ImMe)3]2M(OTf) (M = Ru, 1a; M = Os, 1b) with two tris(N-heterocyclic carbene)borate ligands have been prepared and characterized by ESI-MS, elemental analyses, XPS, and single-crystal X-ray diffraction. X-ray diffraction shows that both complexes display octahedral configuration, in which the metal center is coordinated by two tridentate N-heterocyclic carbene ligands. Electrochemical properties of complexes 1a and 1b have been studied by cyclic voltammetry (CV) measurements, which reveal two reversible redox waves at 0.60, − 0.63 V and 0.35, − 0.86 V for 1a and 1b, respectively, indicating the strong donating nature of the tris(N-heterocyclic carbene)borate ligand.