Syntheses, reactivity, structures and photocatalytic properties of mononuclear ruthenium(II) complexes supported by 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3tacn) ligands

Abstract

Treatment of ruthenium(II) precursor [(Me3tacn)Ru(dmso)Cl2] (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane, dmso = dimethylsulfoxide) (1) with concentrated HCl in the presence of air afforded a ruthenium(III) complex [(Me3tacn)RuCl3·H2O] (2). Reaction of 2, 2,2′-bipyridine or substituted 2,2′-bipyridine, and zinc metal powder in the presence of sodium perchlorate gave the corresponding cationic aquaruthenium(II) complex [(Me3tacn)Ru(R-bpy)(H2O)](ClO4)2 (bpy = 2,2′-bipyridine, R = H, 3; 4,4′-Me2, 4; 5,5′-Me2, 5; 4,4′-di-tBu, 6). The hydrate ligand in complexes 3 and 5 could be substituted by acetonitrile or pyridine forming complexes [(Me3tacn)Ru(5,5′-Me2-bpy)(CH3CN)](ClO4)2 (7) and [(Me3tacn)Ru(R-bpy)(py)](ClO4)2 (py = pyridine, R = H (8), R = 5,5′-Me2 (9), respectively. Interaction of [(Me3tacn)Ru(bpy)(H2O)](PF6)2 with phenylacetylene in methanol afforded a ruthenium-carbene complex [(Me3tacn)(bpy)Ru=C(OMe)CH2Ph](PF6)2 (10). All complexes are well characterized by infrared, UV/Vis, and NMR spectroscopies. The molecular structures of 1, 1·2H2O, 4·2H2O, 7, 8, 9, and 10 have been also established by single-crystal X-ray diffraction. The photocatalysis properties of complexes 3, 5, and 6 for H2 evolution by water splitting were also investigated in the paper.