[tBuLi·(-)-Sparteine]: Molecular Structure of the First Monomeric Butyllithium Compound

摘要

Without doubt n-butyllithium (nBuLi), sec-butyllithium (sBuLi), and tert-butyllithium (tBuLi) are amongst the most important organolithium compounds. However, the high tendency of these compounds towards aggregation, both in solution and in the solid state, hinders the identification of the reactive BuLi species in the reactions of these reagents. nBuLi crystallizes from n-pentane as the hexamer, tBuLi as the tetramer; in the presence of coordinating compounds nBuLi and tBuLi crystallize as tetramers and dimers, respectively. Mixed aggregates of BuLi isomers and lithium amides of alkoxides as well as of BuLi isomers and other organolithium compounds are also known. To simplify the interpretation of reactions with these lithium reagents-and possibly to increase their reactivity-attempts are usually made to suppress their aggregation by the addition of coordinating solvents or compounds. Although the presence of monomeric BuLi derivatives in solution is under discussion, to date no such compound has been characterized in the solid state. Herein we report the preparation of monomeric [tBuLi·(-)-sparteine] (3) and its molecular structure in solid state.