In ethanol the charge-compensated molecule exo-nido-ruthenacarborane [5,6,10-{RuCl(PPh3)(2)}-5,6,10-mu-(H)(3)-10-H-7,8-C2B9H8] reacts with KOH to afford the anionic close-complex [RuH(PPh3)(2)(eta(5)-7,8-C2B9H11)](-) isolated as its K+ (2a) or [K(18-crown-6)](+) (2b) salt. Treatment of 2a with CO gives [Ru(CO)(PPh3)(2)(eta(5)-7,8-C2B9H11)] (3a) in high yield; its structure was determined by X-ray crystallography. In contrast 2b reacts with CO to yield the salt [K(18-crown-6)][RuH(CO)(PPh3)(eta(5)-7,8-C2B9H11)] (2d). Reaction of 2b with [RuCl2(PPh3)(3)] affords [Ru-2(mu-H)(H)(PPh3)(4)(eta(5)-7,8-C2B9H11)] (5), which with CO produces [Ru-2(mu-H)(mu-sigma: eta(5)-7,8-C2B9H10)(CO)(4)(PPh3)(2)] (6), the structure of which was established by X-ray diffraction. The molecule has a metal-metal bond bridged on one side by a hydride ligand and on the other by a nido-7,8-C2B9H10 fragment. The latter is eta(5)-coordinated to a ruthenium atom ligated by a PPh3 and a CO ligand and is also sigma-bonded to the second ruthenium which carries three CO molecules and a PPh3 group. The sigma bond utilizes a boron lying in an alpha site with respect to the carbons in the CCBBB ring coordinated to the Ru(CO)(PPh3) moiety. Reactions between 2b or 2d and [CuCl(PPh3)(3)] and [AuCl(PPh3)], respectively, afford the bimetal complexes [RuM(mu-H)(L)(PPh3)(2)(eta(5)-7,8-C2B9H11)] [M = Cu, L = PPh3 (7a), L = CO (7b); M = Au, L = PPh3 (8a), L = CO (8b)]. X-ray diffraction studies are reported for 7a and 8a, revealing in the case of the former a structure in which an exopolyhedral B-H-Cu bond supplements the Ru(mu-H)Cu interaction.