Hydrocondensation of Carbon Dioxide with Methanol Catalyzed by Anionic Ruthenium Complexes: Isolation, Structural Characterization, and Catalytic Implications of the Dinuclear Anion [Ru2 (CO) 4 ([mu] 2-[eta] 2-CO2CH3) 2 ([mu] 2-OCH3) Cl2]