[H_3–<i>n</i>Fe₄(CO)₁₂(IrCOD)]^<i>n</i>− (<i>n</i> = 1, 2) and [H₂Fe₃(CO)₁₀(IrCOD)]⁻ Bimetallic Fe–Ir Hydride Carbonyl Clusters

The reaction of [HFe4(CO)12]3– (1) with [Ir­(COD)­Cl]2 results in the formation of the bimetallic Fe–Ir monohydride carbonyl cluster [HFe4(CO)12(IrCOD)]2– (2). This is quantitatively protonated by strong acids to the dihydride [H2Fe4(CO)12(IrCOD)]− (3). Further addition of acids to 3 results in the tetranuclear dihydride [H2Fe3(CO)10(IrCOD)]− (4) via formal oxidative elimination of a Fe­(CO)2 fragment. Compounds 2–4 have been fully characterized by means of 1H VT NMR spectroscopy, X-ray crystallography, and DFT calculations. In 2 and 3 the Fe4Ir cluster core adopts a trigonal bipyramidal geometry, while the Fe3Ir core in 4 is tetrahedral. In addition, 1H VT NMR studies indicate that 2 and 3 are fluxional in solution, whereas 4 is not.