Changing the Reactivity of Zero- and Mono-Valent Germanium with a Redox Non-Innocent Bis(silylenyl)carborane Ligand.

Using the chelating C,C'-bis(silylenyl)-ortho-dicarborane ligand, 1,2-(RSi) -1,2-C B H [R=PhC(NtBu) ], leads to the monoatomic zero-valent Ge complex ("germylone") 3. The redox non-innocent character of the carborane scaffold has a drastic influence on the reactivity of 3 towards reductants and oxidants. Reduction of 3 with one molar equivalent of potassium naphthalenide (KC H ) causes facile oxidation of Ge to Ge along with a two-electron reduction of the C B cluster core and subsequent Ge -Ge coupling to form the dianionic bis(silylene)-supported Ge complex 4. In contrast, oxidation of 3 with one molar equivalent of [Cp Fe][B{C H (CF ) } ] as a one-electron oxidant furnishes the dicationic bis(silylene)-supported Ge complex 5. The Ge atom in 3 acts as donor towards GeCl to form the trinuclear mixed-valent Ge →Ge ←Ge complex 6, from which dechlorination with KC H affords the neutral Ge complex 7 as a diradical species.