Fe–Rh and Fe–Ir clusters substituted by diphenylacetylene: Synthesis, solid state structure and electrochemical behaviour of [Fe2Ir2(CO)10(μ4:η2-PhCCPh)]2−, [FeIr2(CO)9(μ3:η2-PhCCPh)], and [Fe2Rh(CO)8(μ3:η2-PhCCPh)]−

The reaction between [Fe2Ir2(CO)12]2− and diphenylacetylene in refluxing CH3CN yields the substituted cluster [Fe2Ir2(CO)10(PhC2Ph)]2− (1). In the crystals, the four metal atoms define a butterfly arrangement whose Ir–Ir hinge is parallel to the acetylenic C2 unit. The neutral triangular cluster [FeIr2(CO)9(PhC2Ph)] (2) is obtained by the treatment of 1 with acids at room temperature; in this 48 valence electrons species, the C–C and the Ir–Ir bonds are also parallel, in the μ3–η∥2 coordination mode.The cluster [Fe2Rh(CO)10]− reacts with diphenylacetylene in refluxing THF yielding [Fe2Rh(CO)8(PhC2Ph)]− (3). In this 46 C.V.E.’s cluster, the C2 unit is perpendicular to the Fe–Fe edge, exemplifying the μ3–η⊥2 bonding mode. According to 13C NMR spectra, the structure of the three clusters is maintained in solution. Electrochemical investigations show that the one-electron oxidation of [Fe2Ir2(CO)10(L)]2− (L = 2CO, PhC2Ph) as well as the one-electron reduction of [Fe2Rh(CO)8(PhC2Ph)]− only generates the respective short lived products.

Graphical abstractThe reactions between diphenylacetylene and [Fe2Ir2(CO)12]2− or [Fe2Rh(CO)10]− yield the substituted clusters [Fe2Ir2(CO)10(PhCCPh)]2− and [Fe2Rh(CO)8(PhCCPh)]−. The first is oxidized by acids to [FeIr2(CO)9(PhCCPh)]. These clusters display different coordination modes of the C–C multiple bond, which always acts as a four-electron donor. Electrochemical studies show that their redox intermediates are short lived.Figure optionsDownload full-size imageDownload as PowerPoint slide