Synthesis and characterization of some new half-sandwich ruthenium(II) complexes with bidentate N,N′-ligands and their application in alcohol oxidation

Abstract

A series of eight new (η6-arene)ruthenium(II) complexes were prepared by the reaction of pyridyl-imine ligands and the ruthenium(II) precursors of the general formula [(η6-arene)Ru(μ-Cl)Cl]2, where arene=p-cymene (1) and C6H6 (2), to form the complexes [(η6-arene)RuCl(C5H4N-2-CHN-Ar)]PF6 (where Ar=2,4,6-trimethylphenyl (a), 2,4-dimethylphenyl (b), 2-methoxyphenyl (c), 2,6-diisopropylphenyl (d)). These complexes were characterized using 1H NMR, 13C NMR, 31P NMR, IR, UV–Vis, HRMS, and TGA. The molecular structures for the complexes 1a,1d, 2a and 2d were determined by single crystal crystallography, revealing a pseudo-octahedral piano stool geometry. In this arrangement, the ruthenium metal is coordinated to the arene ligand at the apex of the stool with one chloride and the N,N-ligand as the base. These complexes were applied as catalysts in the oxidation of cyclic, aliphatic and aromatic alcohols with NaIO4 as oxidant and the complexes showed good conversions and yields to the corresponding carbonyl products.