A WELL-DEFINED SUPPORTED METAL CATALYST - IR4 MGO

[Ir4(CO)12] was used as a precursor for the preparation of a MgO-supported catalyst with a uniquely simple metal structure, Ir4. The precursor was adsorbed on MgO from hexanes with the metal framework remaining intact, as determined by extended X-ray absorption fine structure (EXAFS) spectra. The surface-bound species was inferred to be predominantly [HIr4(CO)11]-, which could be extracted from the surface by cation metathesis and identified in solution by infrared spectroscopy. After treatment of the MgO-supported iridium carbonyl in He followed by H2 at 300 °C, the sample was characterized again by EXAFS spectroscopy; the results provide evidence that the predominant surface species are clusters of four Ir atoms with an average Ir-Ir distance of 2.69 Å. © 1990 J.C. Baltzer A.G. Scientific Publishing Company.