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, [RuI2(RCO2)(CO)4(N∧N)2]+ (N∧N = 2,2‘-bipyridine or 1,10-phenanthroline derivatives) that use RuCl3·3H2O as a starting material. Direct addition of the
bidentate diimine ligand to a methanolic solution of [Ru(CO)2Cl2]n and sodium acetate yielded a mixture of
[RuI2(MeCO2)(CO)4(N∧N)2]+ (N∧N = 4,4‘-dmbpy, and 5,6-dmphen), and [RuII(MeCO2)2(CO)2(N∧N)] (N∧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, [RuII(O2CC6H4)(CO)2(N∧N)], where N∧N = bpy or
phen. A second approach used ligand exchange between a bidentate ligand (N∧N) and the pyridine ligands of
[RuI(RCO2)(CO)2(py)]2 to convert these neutral complexes into [RuI2(RCO2)(CO)4(N∧N)2]+. This method, although it
involved more steps, was applicable for a wider variety of diimine ligands (R = Me and N∧N = 4,4‘-dmbpy,
5,5‘-dmbpy, 5,6-dmphen; R = Ph and N∧N = bpy, phen, 5,6-dmphen).