The resolution of cis-[Ru(phen)2(CH3CN)2]2+ (phen = 1,10-phenanthroline), and its use in the synthesis of chiral cis-[Ru(phen)2X2]n+ species (n = 0, 2; X = CN−, Cl−, py)☆

A convenient general method is described for the isolation of optically active ruthenium(II) complexes, cis-[Ru(phen)2X2]n+. The resolution strategy involves the initial preparation of the Δ and Λ isomers of cis-[Ru(phen)2(CH3CN)2](PF6)2. These precursor compounds were characterized by UV-Vis, 1H NMR and CD spectral analysis, while enantiomeric purity was verified by conversion to optically active [Ru(phen)3]2+. Subsequent nucleophilic displacement of both coordinated CH3CN by X− (where X− = CN−, Cl−, py) proceeds with near complete retention of configuration. The isolation of the optically active neutral species cis-[Ru(phen)2(CN)2] and cis-[Ru(phen)2Cl2] is significant, since the traditional resolution method via diastereoisomer formation is not directly applicable. Furthermore, cis-[Ru(phen)2(CN)2] may serve as a valuable chiral building block for an extensive series of polymetallic complexes where CN− functions as a bridging ligand. The availability of authentic samples of resolved cis-[Ru(phen)2Cl2] is important for the quantitative assessment of stereoselectivity in the covalent binding of such racemic complexes with DNA.