A Bis(silylenyl)pyridine Zero-Valent Germanium Complex and Its Remarkable Reactivity

The synthesis, reactivity, and electronic structure of the unique germylone iron carbonyl complex [SiNSi]Ge⁰→Fe(CO)₄is reported. The compound was obtained in 49 % yield from the reaction of the bis(N-heterocyclic silylenyl)pyridine pincer ligand SiNSi (1,6-C₅NH₃-[EtNSi(N^tBu)₂CPh]₂) with GeCl₂⋅(dioxane) to give the corresponding chlorogermyliumylidene chloride precursor [SiNSi]Ge^IICl⁺Cl⁻, which was further reduced with K₂Fe(CO)₄. Single-crystal X-ray diffraction analysis of [SiNSi]Ge→Fe(CO)₄revealed that the Ge⁰center adopts a trigonal-pyramidal geometry with a Si-Ge-Si angle of 95.66(2)°. Remarkably, one of the Si^IIdonor atoms in the complex is five-coordinated because of additional (pyridine)N→Si coordination. Unexpectedly, the reaction of [SiNSi]Ge→Fe(CO)₄with GeCl₂⋅(dioxane) (one molar equivalent) yielded the first push–pull germylone–germylene donor–acceptor complex, [SiNSi]Ge→GeCl₂→Fe(CO)₄through the insertion of GeCl₂into the dative Ge⁰→Fe bond. The electronic features of the new compounds were investigated by DFT calculations.