Effect of Diphosphine Ligands on the Metal Framework of Carbido Heteronuclear Cluster Compounds:  X-ray Structure of [Fe4Au2C(CO)12(μ-dppm)]·C7H8

The reaction of (NEt4)2[Fe6C(CO)16] and (AuCl)2(μ-L) (L = diphosphine) depends on the nature of the diphosphine. Unexpectedly, for L = dppm (dppm = bis(diphenylphosphino)methane), the cluster [Fe4Au2C(CO)12(dppm)] (1) was formed, whereas for L = dppe (dppe = 1,2-bis(diphenylphosphino)ethane) the reaction gave the 14-metal cluster (Et4N)2[{Fe6AuC(CO)16}2(μ-dppe)], in which two Fe6CAu fragments are linked by the bridging ligand. Remarkably, 1 is a skeletal isomer of the previously published [Fe4Au2C(CO)12(PEt3)2].