Surface-mediated organometallic synthesis:: High-yield syntheses of [Ir4(CO)12], [Ir6(CO)15]2-, and [Ir8(CO)22]2- by controlled reduction of silica-supported IrCl3 or [Ir(cyclooctene)2(μ-Cl)]2 in the presence of Na2CO3 or K2CO3

The controlled reductive carbonylation under 1 arm. of CO of [Ir(cyclooctene)(2)(mu-Cl](2), supported on a silica surface added with an alkali carbonate such as Na2CO3 or K2CO3, can be directed toward the formation of [Ir-4(CO)(12)], K-2[Ir-6(CO)(15)] or K-2[Ir-8(CO)(22)] by controlling (i) the nature and amount of alkali carbonate, (ii) the amount of surface water, and (iii) the temperature. [Ir-4(CO)(12)] can also be prepared by direct controlled reductive carbonylation of IrCl3 supported on silica in the presence of well controlled amounts of Na2CO3. These efficient silica-mediated syntheses are comparable to conventional synthetic methods carried out in solution or on the MgO surface. Like in strongly basic solution or on the MgO surface, 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 reaction conditions and basicity of the silica surface.