Reversible Deformation of SiO2-Supported PtAu6Cluster Induced by the CO Adsorption by In Situ EXAFS

Abstract

Structure and behavior of [(PPh 3 )Pt(AU(PPh 3 )) 6 ](1) supported on SiO 2 surface have been studied by in-situ EXAFS. The structure of the cluster 1 is maintained after deposition on SiO 2 at room temperature. Upon adsorption of CO little change in coordination number for Pt-Au is found in Pt L 3 -edge EXAFS though the coordination number of Au-Au slightly increases in Au L 3 -edge EXAFS and the peak corresponding to Pt(-Au-)P remarkably increases in the Fourier transformation of Pt L 3 -edge EXAFS. We have interpreted the increase in the intensity of the peak oorresponding to Pt(-Au-)P by the multiple scattering effect owing to the change of Pt-Au-P angle. The original EXAFS oscillations are regenerated for both Pt and Au L 3 -edges after the evacuation for 2 h at 353 K accompanied by the desorption of CO. From these EXAFS results and the analogy to the PtAu 6 chemistry in solution, the PtAu 6, framework transforms its structure to a more compact one by CO adsorption with the change in the angle of Pt-Au-P. Unlike the PtAu6 cluster in solution, CO reversibly desorbs from the cluster without collapse of the PtAu 6 framework.