Stability of osmium carbonyl cluster catalysts in different reaction environments

Abstract

There is considerable interest in the nse of organometallic clnster compounds bound to oxide supports as heterogeneous catalysts. In particular, clusters derived from Os3(CO)12 are known to react with terminal OH groups on metal oxides to yield HOs3(CO)10-O-M where M can be Si or Al. In a previous study we have reported high-resolution electron micrographs of such Os3(CO)12 derived catalysts supported on A12O3. We found ca. 0.5 nm scattering centers to be clearly visible in samples that had undergone a 2 hr treatment in flowing Argon at 473 K. The catalysts were characterized by IR spectroscopy and other techniques to establish that the 3 osmium atom triangular framework was intact even on the supported samples. The samples treated in Argon were remarkably stable even under prolonged examination with 100 keV electrons. However, when the catalysts were treated in flowing H2 also at 473 K for 2 hr the resulting particles were unstable and disappeared in the course of extended observation in the microscope.