A carbonyl ligand of [Ru(bpy)2(CO)2](PF6)2 (1) (bpy = 2,2’-bipyridine) or [Ru(bpy)(trpy)(CO)](PF6)2 (2) (trpy = 2,2’:6’,2"-terpyridine) is reversibly converted to hydroxycarbonyl and eta1-CO2 moieties by treatment with OH-. 1 and 2 also react with NaBH4 to afford CH3OH via formyl and hydroxymethyl complexes, and the molecular structures of 2 and [Ru(bpy)2(CO)(CH2OH)]PF6 (3) were determined by X-ray structure analysis. Crystal data : 2, C26H19N5OP2F12Ru, monoclinic, space group C2/c, a = 34.683(3) angstrom, b = 10.168(2) angstrom, c = 24.640(3) angstrom, beta = 133.35(1)-degrees, V = 6318(1) angstrom3, Z = 8, and R = 0.046 (R(W) = 0.060) for 5844 data with F. > 3sigma(F(o)); 3, C22H19N4O2-PF6Ru, monoclinic, space group C2/c, a = 30.931(4) angstrom, b = 7.487(1) angstrom, c = 24.873(3) angstrom, beta = 124.68(1)-degrees, V = 4736(1) angstrom3, Z = 8, and R = 0.059 (R(W) = 0.070) for 2880 data with F(o) >3sigma(F(o)). The controlled-potential electrolysis of 2 at -1.75 V vs AgAg+ in CO2-saturated C2H5OH/H2O (8:2 v/v) at -20-degrees-C produced HC(O)H, CH3OH, H(O)CCOOH, and HOCH2COOH together with CO and HCOOH, while the electrochemical CO2 reduction in the presence of 1 gave only CO and HCOOH under similar electrolysis conditions. The achievement of the multielectron reduction of CO2 by 2 as the first example in homogeneous reactions is ascribed to [Ru(bpy)(trpy)(CHO)]+ formed by two-electron reduction of 2 in protic media.