EFFECT OF PRECURSOR CORE STRUCTURE ON THE HYDROGENATION OF 1,3-BUTADIENE CATALYZED BY CLUSTER-DERIVED MODEL CATALYSTS

The cobalt-carbonyl cluster ligand based complexes, M(2){mu-[(CO)(9)Co -3(mu(3)-CCO2)]}(4), M = Mo, Cu, were converted into active solids by thermolysis. These precursor complexes contain a square planar array o f tricobalt clusters centered by a M(2) carboxylate bridged core which is M-M bonding in the case of M = Mo and nonbonding in the case of M = Cu. TGA, TPD-MS, XPS, BET, and in situ DRIFTS measurements demonstra te the existence of two forms of the resulting materials as well as di fferences in these materials due to precursor structure. The first, fo rmed at 400 K, is designated LT-MCo, M = Mo, Cu, and results from part ial decarbonylation of the precursor with retention of metal carboxyla te linkages. The second, formed at 500 K is designated HT-MCo and resu lts from the full decarbonylation of the precursor and, under H-2, ful l decarboxylation. The catalytic activity of these materials for the h ydrogenation of 1,3-butadiene was studied. Significant differences in the activities and selectivities for the LT- and HT-MCo materials are observed and demonstrate a dependence of catalytic behavior on molecul ar precursor core structure.