Silicon and Germanium Amidinates

The synthesis of novel amidinate silicon and germanium complexes is described. It is shown that the coordination chemistry of amidinate ligands at Si(IV), Ge(II) and Ge(IV) metal centers is strongly influenced by the substituents on the nitrogen and carbon atom. The reaction of different stoichiometric amounts of lithium amidinates with GeCl₄ and Sicl₄ leads to mono-, di- and trisubstituted compounds, while the reaction of 2 equiv. NH(tBu)C(Ph)NLi with GeCl₂.dioxane yields a tetrameric species. Therefore monoanionic, bidentate four-electron donor amidinate ligands are highly suitable for stabilizing low oxidation states and/ or high coordination numbers at group 14 element centers (Si, Ge). A newly synthesized hexacoordinated cis-dichloro-silicon (bis)amidinate complex possibly might be a promising candidate as a precursor for new stable Si(II) compounds.