Syntheses of Geometrical Isomers for Comparison of Properties Caused by Steric and Electronic Effects in Carbonylruthenium(II) Complexes

Both stereoisomers of the novel ruthenium complex [Ru(tpy)(pynp)(CO)](2+) containing 2,2':6',2 ''-terpyridine (tpy), a terminal carbonyl, and the unsymmetrical bidentate naphthyridine ligand 2-(2-pyridyl)-1,8-naphthyridine (pynp) were selectively synthesized. In addition, two more ruthenium complexes [Ru(ptpy)(pynp)(CO)](2+) containing 4'-phenyl-2,2':6',2 ''-terpyridine (ptpy) instead of tpy were also prepared. These complexes were fully characterized and their molecular structures were determined by X-ray crystallography. Some obvious differences between the isomers were revealed by the structural, computational, and spectroscopic results. Furthermore, redox properties and carbonyl ligand-based reactions of these four complexes were examined to evaluate the steric and electronic effects of the other ligands on the carbonyl reactivity. Both effects, based on the structural differences, exerted a large influence on the reactivity.