Pentacoordinated nitrogen atoms in the structure of hexalithium bis[methylsilyl-tris(methylimide)]hexakis (tetrahydrofuran)

Lithiation of tris(methylamino)methylsilane using an excess of n-butyllithi um affords the corresponding trifunctional lithium amide in high yield. The compound crystallizes from tecrahydrofuran as a dimer with six donor molec ules: ( [MeSi(NMeLi)(3)](2)(thf)(6)). The cluster is a cage structure group ed around a crystallographic center of inversion. The silicon and lithium a toms are tetrahedrally tetracoordinated, but the nitrogen atoms are pentaco ordinated and have a square pyramidal environment of one carbon, one silico n, and three lithium atoms. Parallels can be drawn to other species with po lymetallated nitrogen functions. An analogous compound was prepared from tr is(methylamino)vinylsilane.