A novel and generalized approach to the synthesis of ML3n+ [M = ruthenium(II), rhodium(III); L = 2,2'-bipyridine, 1,10-phenanthroline, 2-(arylazo)pyridine; n = 2, 3

Abstract

The chemistry of tris(2,2{prime}-bipyridine)ruthenium(II) and -rhodium(III) complexes and complexes of related ligands has had an extensive literature in recent years. The reason for this is primarily the relevance of this chemistry to photophysical, photochemical, and redox phenomena. But until now, no simple and general synthetic route has been available for the synthesis of such compounds. For example, the tris complex of 2,2{prime}-bipyridine (L{sup 1}) is commonly synthesized by fusion of MCl{sub 3} with the ligand at a very high temperature, whereas the syntheses of the tris complexes of 1,10-phenanthroline (L{sup 2}) and 2-(m-tolyazo)pyridine (L{sup 3}) involve several steps which need extra purification at every stage to eliminate contaminated products. The standard reported synthetic routes are not only lengthy but also cumbersome, and in most of the cases the routes are inefficient. Therefore, there is an obvious need to develop new and direct procedures, of general application, for the synthesis of the important title compounds. In the present report, the authors describe high-yield, single-pot, and general synthetic routes to ML{sub 3}{sup n+} from either hydrated MCl{sub 3} or MCl{sub 2}L{sub 2} (M = Ru(II), Rh(III); L = L{sup 1}-L{sup 3}) and the silver bis complex of the corresponding ligand.