Fe–Rh and Fe–Ir clusters substituted by diphenylacetylene: Synthesis, solid state structure and electrochemical behaviour of [Fe 2Ir 2(CO) 10(μ 4:η 2-PhCCPh)] 2−, [FeIr 2(CO) 9(μ 3:η 2-PhCCPh)], and [Fe 2Rh(CO) 8(μ 3:η 2-PhCCPh)] −

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The reaction between [Fe 2Ir 2(CO) 12] 2− and diphenylacetylene in refluxing CH 3CN yields the substituted cluster [Fe 2Ir 2(CO) 10(PhC 2Ph)] 2− ( 1). In the crystals, the four metal atoms define a butterfly arrangement whose Ir–Ir hinge is parallel to the acetylenic C 2 unit. The neutral triangular cluster [FeIr 2(CO) 9(PhC 2Ph)] ( 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 μ 3 – η ∥ 2 coordination mode. The cluster [Fe 2Rh(CO) 10] − reacts with diphenylacetylene in refluxing THF yielding [Fe 2Rh(CO) 8(PhC 2Ph)] − ( 3). In this 46 C.V.E.’s cluster, the C 2 unit is perpendicular to the Fe–Fe edge, exemplifying the μ 3 – 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 [Fe 2Ir 2(CO) 10(L)] 2− (L = 2CO, PhC 2Ph) as well as the one-electron reduction of [Fe 2Rh(CO) 8(PhC 2Ph)] − only generates the respective short lived products.