Surface-mediated organometallic synthesis: high-yield syntheses of the anion [H3Os4(CO)12]- from [Os(CO)3Cl2]2 or osmium trichloride on the silica surface in the presence of K2CO3

K[H3Os4(CO)12] has been prepared in high yields by reductive carbonylation under rather mild conditions (1 atm and 150°C) of α- [Os(CO)3Cl2]2 or OsCl3 supported on SiO2 in the presence of K2CO3 (molar ratio K2CO3:Os = 10-15:1); in the latter case a two-step process is required. These surface-mediated syntheses of the anionic cluster are more convenient than the traditional ones in solution (higher yields and selectivity) and do not require clusters such as [H4Os4(CO)12] or [Os3(CO)12] as starting materials.