Dilithium hexaorganostannate(IV) compounds.

Hypercoordination of main-group elements such as the heavier Group 14 elements (silicon, germanium, tin, and lead) usually requires strong electron-withdrawing ligands and/or donating groups. Herein, we present the synthesis and characterization of two hexaaryltin(IV) dianions in form of their dilithium salts [Li2(thf)2{Sn(2-py(Me))6}] (py(Me)=C5H3N-5-Me) (2) and [Li2{Sn(2-py(OtBu))6}] (py(OtBu)=C5H3N-6-OtBu) (3). Both complexes are stable in the solid state and solution under inert conditions. Theoretical investigations of compound 2 reveal a significant valence 5s-orbital contribution of the tin atom forming six strongly polarized tin-carbon bonds.