Alkene analogues of bis(N-donor)ketone ligands: ruthenium(II) complexes containing 1-(pyridin-2-yl)-1-(N-methylimidazol-2-yl)ethene and 1,1-bis(N-methylimidazol-2-yl)ethene ((mim)2C=CH2), and structural studies of [Ru(bpy)2{(mim)2C=CH2}][PF6]2 (bpy = 2,2'-bipyridine) and the pyridine-2-carboxylate (pyC02-) complex [Ru(bpy)2(pyC02)][PF6]

Abstract

The complexes [Ru(bpy)2(N~N)][PF6]2 have been synthesized from reactions of cis-[RuCl2(bpy)2].2H20 (bpy = 2, 2'-bipyridine) and the bidentate ligands N~N((mim)2C=CH2 and (py)(mim)C=CH2 where py = pyridin-2-yl and mim = N-methylimidazol-2-yl) in aqueous ethanol; with the analogue (py)(mim)C=O, the pyridine-2-carboxylate complex [Ru(bpy)2(pyC02)][PF6] is formed. The complexes [Ru(bpy)2{(mim)2C=CH2}][PF6] (1) and [Ru(bpy)2(pyCO2)][PF6] (3) characterized by room-temperature single crystal X-ray studies, were shown to have distorted octahedral geometry for ruthenium(II). The (mim)2C=CH2 ligand is non-planar. with the mim mean planes forming a dihedral angle of 32.2(1) and forming dihedral angles of 56.5(1) and 60.4(1)° with the 'C=CC2' mean plane, in contrast to the near planarity reported for the ketone analogue (mim)2C=O in other metal complexes.