Structurally Simple Supported Platinum Clusters Prepared from [Pt15(CO)30]2- on Magnesium Oxide.

Abstract

A Longoni-Chini cluster, [Ptl5(C0),l2-, was prepared on MgO powder by a surfacemediated synthesis from Na2PtCb in the presence of CO. The formation of [Pt15(CO)30]2a-n d its decarbonylation at 120 '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 A 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 PtIS 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 A 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.