Electron Transfer and Chemical Reactions Associated with the Oxidation of an Extensive Series of Mononuclear Complexes [M(CO)~2(kappa^1-P-P)(kappa^2-P-P)X] and Binuclear Complexes [{M(CO)~2(kappa^2-P-P)X}~2(mu-P-P)] (M = Mn, Re; P-P = Diphosphine or Related Ligand; X = Cl, Br)