CHARACTERIZATION AND CATALYSIS OF A SIO2-SUPPORTED [AU6PT] CLUSTER [(AUPPH3)(6)PT(PPH3)](2+) SIO2/

Structures and catalytic properties of a SiO2-supported [Au6Pt] cluste r, [(AuPPh3)(6)Pt(PPh3)](NO3)(2) (1), were characterized by FT-IR, in- situ EXAFS, and TPR, and also by the reactions such as H-2-D-2 equilib ration, ethene hydrogenation, and CO oxidation to get insight into the key issues of metal catalysis. The cluster 1 was supported on SiO2 wi thout fragmentation of the cluster framework at room temperature under Ar atmosphere. The cluster framework of 1/SiO2 was stable up to 400 K under vacuum. EXAFS analysis revealed that after heat-treatment of 1/ SiO2 at 473 K under vacuum the coordination numbers of Pt-Au and Au-Au (Pt) decreased compared to those for the original clusters due to clus ter deformation and after treatment of 1/SiO2 at 773 K the Au particle s and Pt-P-# species (P-#: phosphine species) were produced. The combi nation of TPR and EXAFS showed that the reduction at 603 K caused comp lete cleavage of Pt-Au and Au-P-# bonds accompanied with the formation of Au particles, while Pt-P-# bonds remained at 773 K. The incipient 1/SiO2 showed catalytic activity in H-2-D-2 and ethene hydrogenation a t 303 K without change of the cluster framework. The catalysis of 1/Si O2 was suggested to be referred to the platinum atom which was embedde d in the six gold cluster by the results of CO-adsorption, EXAFS, and pulse reaction analysis. This is contrasted to the fact that both Pt(P Ph3)(4)/SiO2 and [Au-9(PPh3)(8)](NO3)(3)/SiO2 showed no catalytic acti vity for these reactions.