Fe-Rh and Fe-Ir clusters substituted by diphenylacetylene: Synthesis, solid state structure and electrochemical behaviour of [Fe2Ir2(CO)10( 4: 2-PhCCPh)]2-, [FeIr2(CO)9( 3: 2-PhCCPh)], and [Fe2Rh(CO)8( 3: 2-PhCCPh)]-.

The reaction between [Fe2Ir2(CO)12]2- and diphenylacetylene in refluxing MeCN 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) was obtained by the treatment of 1 with acids at room temp.; in this 48 valence-electron species, the C-C and the Ir-Ir bonds are also parallel, in the 3-2.dblvert. coordination mode. The cluster [Fe2Rh(CO)10]- reacts with diphenylacetylene in refluxing THF yielding [Fe2Rh(CO)8(PhC2Ph)]- (3). In this 46 CVE cluster, the C2 unit is perpendicular to the Fe-Fe edge, exemplifying the 3-2 bonding mode. According to 13C NMR spectra, the structure of the three clusters is maintained in soln. Electrochem. studies show that the 1-electron oxidn. of [Fe2Ir2(CO)10(L)]2- (L = 2CO, PhC2Ph) as well as the 1-electron redn. of [Fe2Rh(CO)8(PhC2Ph)]- only generates the resp. short-lived products.