Silicon can form bonds to other tetracoordinated silicon atoms and these bonds form the framework of many organosilicon compounds and crystalline silicon. Silicon can also form a pentacoordinated anionic structure—a so-called ‘silicate’. No compounds containing a direct bond between two silicate moieties—‘disilicates’ where two silicate structures are combined in one species—have been reported because of the electronic repulsion between the anionic halves and difficulty preventing the release of anions. Here we report the synthesis of thermally stable and isolable disilicates by the reductive coupling reaction of a silane bearing two electron-withdrawing bidentate ligands. Two pentacoordinated silicons, positively charged despite the formal negative charge, constitute a single σ-bond and bind eight negatively charged atoms. They can be reversibly protonated, cleaving two Si–O bonds, to afford a tetracoordinated disilane. Their unique electronic properties could be promising for the construction of functional materials with silicon wire made up of silicate chains.
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This work was partially supported by research grants from Yamada Science Foundation, The Japan Securities Scholarship Foundation, the Global COE program, Scientific Research on Priority Area, Creative Scientific Research, and Next Generation Super Computing Project (Nanoscience Project) from the Ministry of Education, Culture, Sports, Science and Technology of Japan, and Research Fellowship from the Japan Society for the Promotion of Science. We thank Tosoh Finechem, Shin-etsu Chemical, and Central Glass for gifts of alkyllithiums, silicon reagents, and fluorine compounds, respectively.
The authors declare no competing financial interests.
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Kano, N., Miyake, H., Sasaki, K. et al. Dianionic species with a bond consisting of two pentacoordinated silicon atoms. Nature Chem 2, 112–116 (2010). https://doi.org/10.1038/nchem.513
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