Reversible Multi-Step and Multielectron Redox Behavior of the Oxo-Centered Trinuclear Ruthenium Complex with Redox-Active Ligand, [Ru3(.mu.3-O)(.mu.-CH3CO2)6(mbpy+)3]4+ (mbpy+ = N-Methyl-4,4'-bipyridinium Ion) and Its Trirhodium and Diruthenium-Rhodium Derivatives