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

Abstract

The controlled reductive carbonylation under 1 atm. of CO of [Ir(cyclooctene)2(μ-Cl)]2, supported on a silica surface added with an alkali carbonate such as Na2CO3 or K2CO3, can be directed toward the formation of [Ir4(CO)12], K2[Ir6(CO)15] or K2[Ir8(CO)22] by controlling (i) the nature and amount of alkali carbonate, (ii) the amount of surface water, and (iii) the temperature. [Ir4(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 [Ir4(CO)12], the first step of nucleation which does not require a strong basicity of the silica surface, gives in a second time sequentially [Ir8(CO)22]2− and [Ir6(CO)15]2− according to reaction conditions and basicity of the silica surface.