Iron-nickel mixed metal clusters: synthesis, reactivity and vibrational spectroscopy of [FeNi5(CO)13]2−. Solid state structure of the anions [FeNi5(CO)13]2− and [Fe3Ni(CO)12]2−

The cluster [FeNi5(CO)13]2 (1) was obtained by reaction of Fe(CO)5 and [Ni6(CO)12]2 (2), in acetonitrile at room temperature. Its solid state structure was determined on the [NEt4] salt, and consists of a trigonally distorted octahedron, with six edge-bridging ligands. This assembly strictly recalls the architecture of the prototypical [Ni6(CO)12]2 anion, by formal replacement of one Ni(CO) unit with the Fe(CO)2 fragment. However, the requirements of the additional ligand have sterical consequences on the other carbonyl groups, which can not be coplanar as in the all-nickel cluster. [FeNi5(CO)13]2 reacts readily with acids, to yield the already known [HFe3Ni(CO)12] (3), and with CO, being stepwise fragmented to species of lower nuclearity, ending with [Fe3Ni(CO)12]2 (4) or [Fe2(CO)8]2. The solid state structure of the tetranuclear [Fe3Ni(CO)12]2 was also determined, and is reported here.