ISOLATION AND STRUCTURE-ANALYSIS OF NEOHEXYLLITHIUM GENERATED BY ETHER CLEAVAGE - PRIMARY AND SECONDARY COORDINATION IN ALKYLLITHIUM AGGREGATES

Ether cleavage of THF at low temperature affords halide-free neohexyll ithium in a two-step reaction via insertion of in situ formed ethylene into the C-Li bond of tert-butyllithium. The crystal structure analys is reveals the formation of tetrameric THF-solvated aggregates in the solid state. The neohexyl ligands adopt a staggered arrangement with r espect to the tetrahedral lithium core, in contrast to the eclipsed co nformation generally observed in unsolvated species. The different con formations in these oligomers can be rationalized readily by distingui shing between primary and secondary cation coordination.