7Li Nuclear Electric Quadrupole Interactions in Alkyllithium Compounds

Abstract

Articles you may be interested inDetermination of the electric quadrupole moment of 7Li by Coulomb scattering of an aligned 7Li beam AIP Conf. Proc. 69, 991 (1981);The 'lLi magnetic resonance in polycrystalline methyllithium-da and ethyllithium-d. was examined at room temperature and at 77°K. The 7Li quadrupole coupling parameters were determined from the quadrupole fine structure of the 'lLi magnetic resonance to be 1 e 2 qQlh 1 =48 kclsec and ' 1 = 0 for methylithium-da and I e2qQlh 1=83 kclsec and '1=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-da because of the difficulties in observing the resonance at 77°K. At room temperature the 7Li magnetic resonance of ethyllithium-d. 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-da displayed no sharp component at room temperature, being like allyllithium, propynyllithium, phenyllithium, fluorenyllithium, and alkoxylithium compounds in this respect.

Multinuclear Residual Quadrupolar Couplings for Structure and Assignment

“…( 7 Li j C Q j ~610 kHz), [77] but in typical fourfold (~tetrahedral) coordination they are again smaller (< 0.01 a. u. or < 100 kHz, respectively). [78] Solid-state 7 Li NMR could show that in alkyl-and aryllithiums, C Q depends on the degree of aggregation and solvation, [79] formation of contact ion pairs [80] or sandwich complexes. [81] Earlier examples of 7 Li RQCs were reported for lithium salts dissolved in surfactant/ alcohol/water lamellar LC phases, [82] phospholipid bicelle solutions, [83] stretched gelatin gels, [40] and N-alkyl imidazoliumbased ionic liquids, [84] where the splitting arises from transient binding to multiple sites on the mesogen or gel and -apart from the phase behaviour or degree of ion pairing -does not confer much structural information.…”