Preparation of coordinatively asymmetrical ruthenium(II) polypyridine complexes

A series of salts of the type cis- [Ru-II(bpy')(bpy ") (CO)(2)](PF6)(2) (bp y' and bpy " represent different bipyridine derivatives) have been prepared by using literature procedures and utilized as precursors for the preparat ion of highly functionalized complexes of Ru-II incorporating neutral and a nionic, mono- and bidentate, nitrogen-, phosphorus- sulfur-, and oxygen-don or ligands. The new synthetic approach builds upon previous work with the I trimethylamine N-oxide-assisted removal of the carbonyl ligand. Difficulti es with the use of this potent oxidant in the presence of reducing ligands such as dppe and nitrite have been overcome by the use of acetonitrile comp lexes of the type cis-[Ru(bpy')(bpy ")(CH3CN)(2)](2+) and pyridine complexe s of the type cis-[Ru(bpy')(bpy ")(py)(2)](2+) as highly versatile intermed iates. Strategies for the selective removal of a single carbonyl ligand fro m the precursors have been developed and used to synthesize the highly asym metrical complexes cis- [Ru-II(bpy')(bpy ")(py)(CO)](2+) and cis-[Ru-II(bpy ') (bpy ") (py)(NO)](3+). The synthetic chemistry has been extended by usin g either of these complexes and the complex-as-ligand strategy to prepare t he pyrazine-bridged complex cis,cis- [(Ru-II(bpy')(bpy ") (py))(2)(pz)]-(PF 6)(4) (pz is pyrazine). Finally, a methodology for the preparation of isoth iocyanate complexes such as cis-Ru(bpy')(bpy ")(NCS)(2) has been developed. For the pyridyl/carbonyl, pyridyl/nitrosyl, and ligand-bridged complexes, geometrical isomers were formed in statistical yields. For the isothiocyana te complex cis-Ru(dmb)(4,4'-(COOEt)(2)bpy)(NCS)(2), the majority (N,N-bound ) isomer was isolated from the other three linkage isomers. For all the syn theses reported, yields were high, 44-96%, and each procedure appears to be both general and redundant in that multiple schemes are, possible for the preparation of most targets.