Structural Studies of Fluorenyllithium Complexes Using 7Li SolidState NMR Spectroscopy

Abstract

The effect on the solid-state 7Li chemical shifts and quadrupolar coupling constants of different locations of the lithium cation relative to the carbanion framework of delocalized carbanions was investigated. When the lithium cation is situated above the conjugated system, the chemical shift is about -7 ppm as expected, and around -2 ppm otherwise. The quadrupolar coupling constant is very sensitive to changes in the lithium cation position and to changes in coordination. The value varies between 27 and 262 kHz. A combination of chemical shifts and quadrupolar coupling constants is necessary to retrieve the correct structural information.