7Li Nuclear Electric Quadrupole Interactions in Alkyllithium Compounds

Abstract

The 7Li magnetic resonance in polycrystalline methyllithium-d3 and ethyllithium-d5 was examined at room temperature and at 77°K. The 7Li quadrupole coupling parameters were determined from the quadrupole fine structure of the 7Li magnetic resonance to be | e2qQ/h | = 48 kc/sec and η = 0 for methylithium-d3 and | e2qQ/h | = 83 kc/sec and η = 0.79 for ethyllithium-d5. The quadrupole coupling is independent of temperature for ethyllithium-d5, but the temperature dependence of the coupling is uncertain for methyllithium-d3 because of the difficulties in observing the resonance at 77°K. At room temperature the 7Li magnetic resonance of ethyllithium-d5 exhibits a narrow component, 87 cps broad, superimposed upon the broad, quadrupolar split line. This sharp component, which is similar to that observed in isopropyllithium, t-butyllithium, and neopentyllithium, is not observed at 77°K and is presumably due to motional narrowing. The 7Li resonance of methyllithium-d3 displayed no sharp component at room temperature, being like allyllithium, propynyllithium, phenyllithium, fluorenyllithium, and alkoxylithium compounds in this respect.