Generation of a supported iridium catalyst of extremely high dispersion

Abstract

THE preparation of supported metallic catalysts in a very high state of dispersion—that is, with a very small average metallic particle size—is of considerable current interest. Not only is the surface area per unit mass of metal thus increased, but if the metallic particles are sufficiently small, their intrinsic catalytic properties may be different from those of the massive metal. On the whole, changes of the latter sort seem to be found when the particle diameter is less than about 2 nm (refs 1, 2). The use of a metallic cluster carbonyl (MCC) as a means of preparing a dispersed metallic catalyst has been the subject of preliminary exploration^3,4,5. Although it was indicated that this route could yield highly dispersed metal, it was clear³ that considerable cluster aggregation occurred during thermal decarbonylation and hydrogen reduction (at 573 K). This note reports the preparation from Ir ₄ (CO)₁₂ of a supported iridium catalyst in a very high state of dispersion.