Preparation,crystal structures and properties of half-sandwich ruthenium complexes containing salicylbenzoxazole ligands

Three half-sandwich ruthenium complexes [Ru(p-cymene)LCl] containing salicylbenzoxazole ligands [LH = 2-(5-methyl-benzoxazol-2-yl)-4-methyl-phenol (2a), LH = 2-(5-methyl-benzoxazol-2-yl)-4-chloro-phenol (2b), and LH = 2-(5-methyl-benzoxazol-2-yl)-4-bromo-phenol (2c)] were synthesized and characterized. All half-sandwich ruthenium complexes were fully characterized by ¹H and ¹³C NMR spectra, MS, elemental analyses, and UV–vis as well as cyclic voltammetry (CV). The molecular structures of 2a, 2b, and 2c were confirmed by single-crystal X-ray diffraction. Single-crystal X-ray structures show that the synthesized ruthenium complexes are three-legged piano-stools with a six-membered metallocycle formed by coordination of the bidentate salicylbenzoxazole ligands to the metal centers. Data from CV and UV–vis absorption of the ruthenium complexes indicated that by changing the substituent on the para position of (donating or withdraw group) the salicylbenzoxazole ligands, minor changes in redox and electronic properties of the ruthenium complexes were observed.