Comparative structural description of five arene ruthenium(II) complexes of N,N-bidentate Schiff base ligands to related complexes from literature

Abstract

A series of new half-sandwich Ru(II) complex salts of the general formula [(η6-arene)RuX(L)]PF6 (where arene = p-cymene, X = Br and ligand L1 = N-tert-butyl-N-(pyridyl methylene) amine (complex 1), ligand L2 = N-isopropyl-2-pyridine carbaldimine (complex 2), ligand L3 = (2,5-dimethyl-phenyl)-pyridin-2-yl methylene amine (complex 3), ligand L4 = (3,5-dimethyl-phenyl)-pyridin-2-yl methylene (complex 4) and arene = C6H6, X = I, ligand L5 = (4-bromo-phenyl)-pyridin-2-yl methylene (complex 5) have been synthesized by reacting the ruthenium arene precursors [(η6-arene)Ru(μ-X)X]2 with N,N-bidentate ligands in a 1:2 ratio. Full characterization of the complexes was accomplished by physicochemical and spectroscopic methods and X-ray structures of all the complexes 1–5. The crystal structures reveal that the ruthenium centers in 1–5 are coordinated to the N,N-bidentate ligand in a bidentate manner, to the respective halide, and to the arene ring to give a pseudo-tetrahedral geometry around them. The whole arrangement is referred to as the three-legged piano stool, in which the N,N-bidentate ligand and the halide (Br or I) serve as the base occupying three coordination sites, while the arene ring serves as the apex of the stool and occupy the remaining coordination sites.