Carbonyl-carboxylato-ruthenium complexes incorporating diimine ligands and unexpected cyclometalation of carboxylate ligands.

We report two new synthetic routes to the dinuclear Ru(I) complexes, Ru(I)(2)(RCO(2))(CO)(4)(N( wedge )N)(2) (N( wedge )N = 2,2'-bipyridine or 1,10-phenanthroline derivatives) that use RuCl(3).3H(2)O as a starting material. Direct addition of the bidentate diimine ligand to a methanolic solution of Ru(CO)(2)Cl(2) and sodium acetate yielded a mixture of Ru(I)(2)(MeCO(2))(CO)(4)(N( wedge )N)(2) (N( wedge )N = 4,4'-dmbpy, and 5,6-dmphen), and [Ru(II)(MeCO(2))(2)(CO)(2)(N( wedge )N)] (N( wedge )N = 4,4'-dmbpy and 5,5'-dmbpy). Single-crystal X-ray studies confirmed that the Ru(II) complexes had a trans-acetate-cis-carbonyl arrangement of the ligands. In contrast, the use of sodium benzoate resulted in the unexpected formation of a Ru-C bond producing ortho-cyclometalated complexes, [Ru(II)(O(2)CC(6)H(4))(CO)(2)(N( wedge )N)], where N( wedge )N = bpy or phen. A second approach used ligand exchange between a bidentate ligand (N( wedge )N) and the pyridine ligands of Ru(I)(RCO(2))(CO)(2)(py) to convert these neutral complexes into Ru(I)(2)(RCO(2))(CO)(4)(N( wedge )N)(2). This method, although it involved more steps, was applicable for a wider variety of diimine ligands (R = Me and N( wedge )N = 4,4'-dmbpy, 5,5'-dmbpy, 5,6-dmphen; R = Ph and N( wedge )N = bpy, phen, 5,6-dmphen).