A Zwitterionic Heterobimetallic Gold–Iron Complex Supported by Bis(N‐Heterocyclic Imine)Silyliumylidene

The facile synthesis of the first bis‐N‐heterocyclic imine‐stabilized chlorosilyliumylidene 1 is reported. Remarkably, consecutive reaction of 1 with PPh3AuCl and K2Fe(CO)4 gives rise to the unique heterobimetallic complex 1,2‐(MesNHI)2‐C2H4‐ClSiAuFe(CO)4 (4). The overall neutral complex 4 bears an unusual linear Si−Au−Fe structure and a rare anagostic interaction between the d10‐configured gold atom and a CH bond of the mesityl ligand. According to the computational analysis and 57Fe Mössbauer spectroscopy, the formal Fe‐oxidation state remains at −II. Thus, the electronic structure of 4 is best described as an overall neutral—yet zwitterionic—heterobimetallic “Si(II)+‐Au(I)+‐Fe(‐II)2−”‐silyliumylidene complex, derived from double anion exchange. The computational analysis indicates strong hyperconjugative back donation from the gold(I) atom to the silyliumylidene ligand. The selective synthesis of a silyliumylidene‐stabilized mononuclear Au−Fe complex, by a convenient one‐pot reaction starting from bis‐NHI silyliumylidene chloride, is reported. X‐ray crystallography, IR and 57Fe Mössbauer spectroscopy, as well as computations suggest a zwitterionic Si(II)+−Au(I)+−Fe(‐II)2− bonding motif with rare anagostic CH⋅⋅⋅Au contacts and considerable backbonding capabilities of the silyliumylidene.