Surface-Mediated Organometallic Synthesis: The Activating Role of Silica for a High-Yield Route to [H4Os4(CO)12] and [HOs3(CO)10Y] (Y = OH, OR, Cl, Br, I, O2CR, SCN) Clusters from [Os3(CO)12]

Activation of [Os 3 (CO) 12 ] by the silica surface via reaction with surface silanol groups provides a new convenient general approach to the selective, high-yield synthesis of various osmium carbonyl clusters such as [H 4 Os 4 (CO) 12 ] and [HOs 3 (CO) 10 Y] (Y = a three-electron donor such as OH, OR, Cl, Br, I, O 2 CR, and SCN). These silica-mediated syntheses compare favorably with the more conventional syntheses in solution because (i) differently from other related intermediates used in solution, silica-anchored [HOs 3 (CO) 10 (OSi⋮)] is easily obtained in quantitative yield starting from [Os 3 (CO) 12 ] in one step and (ii) the conversion of [HOs 3 (CO) 10 (OSi⋮)] occurs in one pot usually in high yields and under mild reaction conditions. In addition, the related species [HOs 3 (CO) 10 (OH)], which can be obtained almost quantitatively by hydrolysis of [HOs 3 (CO) 10 (OSi⋮)], is even more reactive than its precursor and allows a three-step synthesis of various osmium clusters characterized by excellent total yields from [Os 3 (CO) 12 ].