Surface-mediated organometallic synthesis: High-yield syntheses of [Ir-4(CO)(12)], [Ir-6(CO)(15)](2-), and [Ir-8(CO)(22)](2-) by controlled reductionof silica-supported IrCl3 or [Ir(cyclooctene)(2)(mu-Cl)](2) in the presence of Na2CO3 or K2CO3

The controlled reductive carbonylation under 1 arm. of CO of [Ir(cycloocten e)(2)(mu-Cl](2), supported on a silica surface added with an alkali carbona te such as Na2CO3 or K2CO3, can be directed toward the formation of [Ir-4(C O)(12)], K-2[Ir-6(CO)(15)] or K-2[Ir-8(CO)(22)] by controlling (i) the natu re and amount of alkali carbonate, (ii) the amount of surface water, and (i ii) the temperature. [Ir-4(CO)(12)] can also be prepared by direct controll ed reductive carbonylation of IrCl3 supported on silica in the presence of well controlled amounts of Na2CO3. These efficient silica-mediated synthese s are comparable to conventional synthetic methods carried out in solution or on the MgO surface. Like in strongly basic solution or on the MgO surfac e, the initially formed [Ir-4(CO)(12)], the first step of nucleation which does not require a strong basicity of the silica surface, gives in a second time sequentially [Ir-8(CO)(22)](2-) and [Ir-6(CO)(15)](2-) according to r eaction conditions and basicity of the silica surface.