STRUCTURALLY SIMPLE SUPPORTED PLATINUM CLUSTERS PREPARED FROM [PT15(CO)30]2- ON MAGNESIUM-OXIDE

A Longoni-Chini cluster, [Pt15(CO)30]2-, was prepared on MgO powder by a surface-mediated synthesis from Na2PtCl6 in the presence of CO. The formation of [Pt15(CO)30]2- and its decarbonylation at 120-degrees-C under vacuum were characterized by infrared and X-ray absorption spectroscopies. The decarbonylated cluster had an average Pt-Pt bond distance of 2.76 angstrom and an average Pt-Pt first-shell coordination number of 3.7, indicating that the trigonal prismatic framework structure of the Longoni-Chini cluster was retained after decarbonylation; thus the decarbonylated cluster is represented as Pt15 with a trigonal prismatic structure. When this sample was recarbonylated, the Longoni-Chini cluster was not re-formed. The average Pt-Pt bond distance increased to 2.78 angstrom and the Pt-Pt first-shell coordination number increased to 6.0, indicating that a CO-induced morphology change gave approximately hemispherical Pt clusters with adsorbed CO.