Reversible deformation of SiO2-supported PtAu6 cluster induced by the CO adsorption by in situ EXAFS

structure and behavior of [(PPh3)Pt(Au(PPh3))(6)](1) supported on SiO2 surface have been studied by in-situ EXAFS. The structure of the cluster 1 is maintained after deposition on SiO, 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 corresponding 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 PtAu6 chemistry in solution, the PtAu6 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 PtAu6 framework.