IR STUDIES OF THE THERMAL DECOMPOSITION OF[Rh6（CO）16+Co4（CO）12]/SiO2: EVIDENCE FOR THE FORMATION OF RhCo3（CO）12/SiO2

Thermal decomposition of [Rh6(Co)16+Co4(Co)12]/SiO2,Ph6(CO)16/SiO2 and Co4(CO)12/SiO2 under a static hydroformylation atmosphere (C2H4:CO:H2=6.5:6.5:6.5 kPa) have been investigated by means of IR spectroscopy. Rh6(CO)16 is thermally more stable than Co4(CO)12 on the SiO2 surface. RhCo3(CO)12 is formed by the direct reaction between Rh6(CO)16 and Co4(CO)12 on the SiO2 surface at 423~473 K. Comparison of the thermal stabilities of supported Rh6(CO)16 and Co4(CO)12 suggests that the surface reaction producing RhCo3(CO)12 proceeds via decarbonylation of Co4(CO)12. Spectroscopic results under C2th+CO+H2 and Under CO alone show that the formation of RhCo3(CO)12 from monometallic clusters is influenced by the atmosphere used.