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 PPh3 AuCl and K2 Fe(CO)4 gives rise to the unique heterobimetallic complex 1,2-(Mes NHI)2 -C2 H4 -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 57 Fe 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.