Molecular low-oxidation-state chemistry with tetra-anionic group 14 elements

Abstract The group 14 tetrel elements carbon, silicon, germanium, tin and lead need to lose or gain four electrons to reach a stable full-valence shell. However, despite fulfilling the octet rule, tetra-anionic tetrels are highly reactive anions. The considerable 4− charge on single atoms dictates their chemistry, making such anions highly reducing, nucleophilic or strongly basic. Here we report facile full reduction of silicon, germanium, tin and lead precursors to tetra-anions using a molecular Mg 0 complex at room temperature. These anions, which are stabilized by a crown consisting of metal cations and bridging ligands, are in the −IV oxidation state. They are found to be strong Brønsted bases and can react as quadruple nucleophiles or eight-electron reducing agents. This work extends the low-valent chemistry of tetrel complexes to its ultimate negative oxidation state.