Molecular organoosmium chemistry and catalysis on the basic magnesium oxide surface

The complex (H/sub 2/Os(CO)/sub 4/) is deprotonated upon adsorption on the basic surface of magnesia. The resulting (HOs(CO)/sub 4/)/sup -/ is held strongly to the surface by a localized carbonyl-Mg/sup 2 +/ interaction analogous to the contact anion ion pairing observed for (Na)(HOs(CO)/sub 4/) in THF. The surface-bound complex is the precursor of surface species that are catalytically active for CO hydrogenation to give methane and higher hydrocarbons at 275 /sup 0/C and 10 atm. During catalysis, the mononuclear anion is transformed into the stable (H/sub 3/Os/sub 4/(CO)/sub 12/)/sup -/ and (Os/sub 10/C(CO)/sub 24/)/sup 2 -/, which become the only surface species detected by infrared spectroscopy and by extraction of surface-bound anions. The chemistry of the molecular condensation reactions of osmium carbonyls on the basic magnesia surface closely parallels that of osmium carbonyls in basic solution. The tetranuclear osmium cluster is suggested to be involved in the CO hydrogenation catalysis. 51 references, 12 figures, 1 table.