Redox Behavior Of The Electronically Unsaturated Clusters Os3(Mu-H)2(Co)9l And Their Saturated Congeners Os3(Mu-H)(H)(Co)10l (L = Co, Pph3, Asph3)

The 46 e cluster Os3(mu-H)2(CO)10 exhibits a very complex redox behavior. Its cyclic voltammetric (CV) response consists of two reduction peaks, the latter having an adsorption character. Polarographic, coulometric, and spectroscopic data indicate that the initially electrogenerated monoanion [Os3H2(CO)10]- undergoes several chemical side reactions, one being an irreversible cluster breakdown and the others being dimerization reactions. The adducts Os3(H)(mu-H)(CO)10L with Lewis bases (L = CO, PPh3, AsPh3) exhibit a single 2e, chemically irreversible reduction process at more negative potentials than Os3H2(CO)10. Their electrochemical behavior is similar to that of the saturated cluster Os3(CO)12. Elimination of one CO on thermolysis produces Os3H2(CO)9L (L = PPh3, AsPh3) where the unsaturated system Os-H-2-Os is restored; accordingly its CV response is very similar to that of the parent compound, Os3H-2(CO)10.