Tris(trimethylsilyl)‐Substituted Heavy Group 14‐Element‐Centered Anions: Unsolvated Trimeric Germyllithium and Solvated Dimeric Silyl‐ and Stannyllithiums

Abstract

AbstractTris(trimethylsilyl)‐substituted group 14‐element‐centered anion monomers [LiE(SiMe3)3·3THF] (E = Si, Ge, and Sn) can be distilled under reduced pressure to give dimeric silyllithium 4 and stannyllithium 6, and trimeric germyllithium 5 without pyrolysis products such as dilithiometallanes. The molecular structures of 4, 5, and 6 were unequivocally determined by X‐ray diffraction. Dimer 4 has a symmetrical bent four‐membered‐ring structure consisting of two anionic silicon atoms and two cationic lithium atoms with coordinated THF molecules. Dimer 6 has an unsymmetrical distorted four‐membered‐ring structure consisting of two anionic tin atoms, a bridged unsolvated lithium atom, and a bridged lithium atom solvated by a THF molecule. Interestingly, 6 aggregates to form dimers of dimers by an intermolecular CH3···Li interaction. Trimeric germyllithium 5 forms an equilateral triangular lithium cluster without solvation. Compound 5 has a crystallographic threefold axis with three anionic germanium atoms and three cationic lithium atoms lying in the same plane. The lithium atoms in 5 are stabilized by an intramolecular CH3···Li interaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)