Isolation and structure determination of a tetrameric sulfonyl dilithio methandiide in solution based on crystal structure analysis and 6Li/13C NMR spectroscopic data.

Jürgen Vollhardt,Hans Jörg Lindner,Hans-Joachim Gais

doi:10.3762/bjoc.16.172

Abstract

Dilithio sulfonyl methandiides are a synthetically and structurally highly interesting group of functionalized geminal dianions. Although very desirable, knowledge of the structure of dilithio methandiides in solution was lacking up to now. Herein, we describe the isolation and determination of the structure of tetrameric dilithio (trimethylsilyl)(phenylsulfonyl) methandiide in solution and in the crystal. The elucidation of the structure of the tetramer is based on crystal structure analysis and 13C/6Li NMR spectroscopic data. A characteristic feature of the structure of the tetramer is the C2 symmetric C–Li chain, composed of four doubly Li-coordinated dianionic carbon and five Li atoms. Three Li atoms are devoid of a contact to a dianionic C atom. The tetramer, the dianionic C atoms of which undergo fast exchange, is in THF solution in fast equilibrium with a further aggregate, which is stable only at low temperatures.

Highlights

Functionalized dilithio methandiides I–III (Figure 1) are a fascinating class of compounds, whose reactivity, synthetic potential, and structure have received much interest in organic and metalorganic chemistry [1,2]
An X-ray crystal structure analysis had shown a Ci symmetric hexamer, (2a)6·Li2O·(THF)6, the dianionic C atoms of which are each coordinated by two Li atoms in a nonplanar fashion [15]
Lithium atoms Li3 and Li5, which are each coordinated by two dianionic carbon atoms, have planar trigonal coordination geometry

Summary

Introduction

Functionalized dilithio methandiides I–III (Figure 1) are a fascinating class of compounds, whose reactivity, synthetic potential, and structure have received much interest in organic and metalorganic chemistry [1,2]. A characteristic feature of the structure of the tetramer is the C2 symmetric C–Li chain, composed of four doubly Li-coordinated dianionic carbon and five Li atoms. The tetramer, the dianionic C atoms of which undergo fast exchange, is in THF solution in fast equilibrium with a further aggregate, which is stable only at low temperatures.

Results

Conclusion