Surface-Mediated Organometallic Synthesis: Preparation of [Os5C(CO)14]^2- and [Os10C(CO)24]^2- on the Basic Magnesium Oxide Surface

High-nuclearity osmium carbonyl clusters have been synthesized by simple means and in high yields on the surface of porous, high surface area magnesium oxide in the presence of CO and CO + H2. Control of the product distributions was exerted by choice of the temperature, pressure, gas-phase composition, and metal compound precursor. [Os10C(CO)24]2- was prepared from [H2OScl6] adsorbed on MgO treated in equimolar CO + H2 at 275 °C and 1 atm, and [Os5C(co)14]2- was prepared from [Os3(CO)12] adsorbed on MgO treated in CO at 275 °C and 1 atm. These cluster anions were isolated from the MgO in 65% yield by cation metathesis with [PPN] [Cl] in acetone. These syntheses are more efficient than the best known solution syntheses; the results suggest a more general applicability of surface-mediated synthesis. © 1989, American Chemical Society. All rights reserved.