Fe-Rh and Fe-Ir clusters substituted by diphenylacetylene: synthesis, solid state structure and electrochemical behaviour of [Fe2Ir2(CO)10(m4:h2-PhCCPh)]2-, [FeIr2(CO)9(m3:h2-PhCCPh)], and [Fe2Rh(CO)8(m3:h2-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 s(-) 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 s(-) 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. © 2008 Elsevier B.V. All rights reserved.