FORMATION OF OPTICALLY-ACTIVE [RU(BIPY)2CL2] (BIPY = 2,2'-BIPYRIDYL) BY PHOTODISSOCIATION OF [RU(BIPY)3]CL2 IN DICHLOROMETHANE

An optically active bis-chelated complex, [Ru(bipy)2Cl2] (bipy = 2,2'-bipyridyl), has been obtained when enantiomeric [Ru(bipy)3]Cl2 was illuminated by visible light in dichloromethane. From the dependence of the optical purity of the product on light intensity, it is proposed that the reaction from DELTA-[Ru(bipy)3]Cl2 to DELTA-[Ru(bipy)2Cl2] (Chirality retention) proceeds by way of the dissociation of a monodentate ligand, bipy*, from a photoactivated intermediate, DELTA-[Ru(bipy)2(bipy*)Cl]Cl in the dark, while the reaction to LAMBDA-[Ru(bipy)2Cl2] (chirality inversion) involves the further photoactivated configurational change of DELTA-[Ru(bipy)2(bipy*)Cl]Cl to LAMBDA-[Ru(bipy)2(bipy*)Cl]Cl. Racemization is avoided under the conditions of weak light and high temperature. The synthetic value of optically active [Ru(bipy)2Cl2] as a chiral intermediate has been exemplified by preparing a new chiral amphiphilic ruthenium(II) complex.