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

Abstract

The synthesis, reactivity, and electronic structure of the unique germylone iron carbonyl complex [SiNSi]Ge⁰ →Fe(CO)₄ is reported. The compound was obtained in 49 % yield from the reaction of the bis(N-heterocyclic silylenyl)pyridine pincer ligand SiNSi (1,6-C₅ NH₃ -[EtNSi(N^t Bu)₂ CPh]₂ ) with GeCl₂ ⋅(dioxane) to give the corresponding chlorogermyliumylidene chloride precursor [SiNSi]Ge^II Cl⁺ Cl^- , which was further reduced with K₂ Fe(CO)₄ . Single-crystal X-ray diffraction analysis of [SiNSi]Ge→Fe(CO)₄ revealed that the Ge⁰ center adopts a trigonal-pyramidal geometry with a Si-Ge-Si angle of 95.66(2)°. Remarkably, one of the Si^II donor atoms in the complex is five-coordinated because of additional (pyridine)N→Si coordination. Unexpectedly, the reaction of [SiNSi]Ge→Fe(CO)₄ with GeCl₂ ⋅(dioxane) (one molar equivalent) yielded the first push-pull germylone-germylene donor-acceptor complex, [SiNSi]Ge→GeCl₂ →Fe(CO)₄ through the insertion of GeCl₂ into the dative Ge⁰ →Fe bond. The electronic features of the new compounds were investigated by DFT calculations.

Keywords: germanium; metallylenes; pincer ligands; silicon; silylene.