Cluster chemistry on surfaces: Characterization and catalytic studies of phosphine-stabilized platinum-gold clusters on silica and alumina supports

摘要: Cationic, phosphine-ligated Pt-Au cluster compounds, [Pt(AuPPh{sub 3}){sub 8}](NO{sub 2} (1) and [(PPh{sub 3})Pt(AuPPh{sub 6}](NO{sub (2), have been immobilized on silica alumina supports. Characterization of the supported clusters by {sup 31}P MAS NMR, IR, UV-visible spectroscopy study chemisorption temperature-programmed desorption CO show that are intact without measurable fragmentation or irreversible transformation. This is confirmed quantitative clusters. The reactivity with H{sub was found to be similar known reactivities in solution molecular solid phases. 3})-Pt(H)(AuPPh{sub 7}](NO{sub (3) also MAS{sup NMR experiments. turnover rate (TOR) for 2}-D{sub equilibration determined these at room temperature. 1 2 were good catalysts supports after treatment 135{degrees}C under vacuum (TOR = 10-20 s{sup -1}), but showed significant activation 110{degrees}C 85-220 -1}). Cluster 3/SiO{sub gave a 170 -1}) no thermal activation. All samplesmore » subjected thermolysis conditions given above could quantitatively desorbed. high activities believed result from support-promoted, partial PPh{sub 3} dissociation. Desorption experiments shows this dissociation reversible.« less