Ruthenium(II) alpha-diimide complexes with one, two, and three 4,4 '-bis(hydroxymethyl)-2,2 '-bipyridine and 4,4 '-bis(chloromethy1)-2,2 '-bipyridineligands: Useful starting materials for further derivatization

Although Ru(II) tris(bipyridine) complexes and related a-diimine analogues find wide use in chemistry, many common ligand and metal complex derivative s are difficult to synthesize. The halomethyl bpy ligands and their inert m etal complexes are one such example. These compounds are desirable since th ey serve as useful starting materials for a variety of more elaborate deriv atives. Although 4,4'-bis(halomethyl)-2,2'-bipyridine ligands readily chela te to labile metal ions, they are not compatible with the higher temperatur es and polar solvents typically required to effect ligand substitution at m ore inert Ru centers. Alternate routes to these targets involving solvento and other substitution labile intermediates yield products, but yields are typically low due to difficulties in purification. This report describes a new route to Ru(II) halomethyl bpy complexes involving chelation of the mor e robust 4,4'-bis (hydroxymethyl) -2,2'-bipyridine, bpy(CH2OH)(2), followed by conversion to the corresponding chloromethyl species on the metal using oxalyl chloride and DMF in THF or CH3CN solution. This new "OH to Cl" meth odology is demonstrated for Ru(II) complexes with two, four, and six functi onalities with both bpy and phen ancillary ligands. Complexes of the genera l formula [LnRu{bpy(CH2X)(2)}(3-n)](PF6)(2) (L = bpy, phen; X = OH, Cl; n = 0-2) have been prepared in good yield and are conveniently purified by pre cipitation. These Ru alpha-diimine complexes have already been utilized as multifunctional metalloinitiators for controlled cationic and radical polym erizations. They promise to be valuable for bpy derivatization generally.