Solid-state NMR spectroscopy and ab initio calculations of some base-free organolithium compounds

dc.contributor.advisorPenner, Glenn H.
dc.contributor.authorChang, Phillis
dc.date.accessioned2020-08-24T15:49:29Z
dc.date.available2020-08-24T15:49:29Z
dc.date.copyright2001
dc.degree.departmentDepartment of Chemistry and Biochemistryen_US
dc.degree.grantorUniversity of Guelphen_US
dc.degree.nameDoctor of Philosophyen_US
dc.description.abstractThis thesis is an investigation of the electronic structures for several base-free organolithium compounds using solid-state 6Li, 7Li, and 13C nuclear magnetic resonance spectroscopy and 'ab initio' calculations. NMR measurements of lithium chemical shift anisotropies ([Delta][sigma]) and nuclear quadrupolar coupling constants ([chi]) have been performed on solid samples of 't'-butyllithium (tBuLi), cyclopentadienyllithium (CpLi), penta-methylcyclopentadienyllithium (Cp*Li), 2,4,6-tri(isopropyl)phenyllithium (iPr3PhLi), and propynyllithium (PpLi). Of the various compounds examined, only in CpLi, Cp*Li, and iPr 3PhLi are the [Delta][sigma] values for lithium large enough to be measured. From spectral simulations, values of [Delta][sigma] = 42 ± 2 ppm, [Delta][sigma] = 45 ± 2 ppm, and [Delta][sigma] = 26 ± 2 ppm have been determined respectively for CpLi, Cp*Li, and iPr3PhLi. Moreover, 7 Li [chi] values of 100 ± 3 kHz, 11 ± 1 kHz, 18 ± 1 kHz, 323 ± 1 kHz, and 35 ± 2 kHz have been obtained for tBuLi, CpLi, Cp*Li, iPr3PhLi, and PpLi, respectively. It has been found that the 'ab initio' calculations of [Delta][sigma] and [chi] values do not agree with the measurements unless the solid-state structures are employed. Furthermore, computational studies have been carried out on MeLi and PhLi utilizing, correspondingly, their tetrameric and dimeric solid structures as reported in the literature. In the case of PpLi, whose crystal structure, to the best of our knowledge, has not been established, several models, having Td, C4h, and S4 symmetry, have been proposed. Unfortunately the NMR parameters calculated using these geometries do not agree with the experiments, and the solid PpLi structure remains unsolved. In addition to structural information, the dynamics of lithium atom exchange and Cp ring rotation in tBuLi and CpLi, respectively, have been studied. For lithium atom exchange in solid tBuLi, Ea = 23.8 ± 0.1 kJ/mol for the high-temperature phase and Ea = 23.0 ± 0.6 kJ/mol for the low-temperature phase. For Cp ring rotation in solid CpLi, Ea = 26.3 ± 0.3 kJ/mol.en_US
dc.identifier.urihttps://hdl.handle.net/10214/20270
dc.language.isoen
dc.publisherUniversity of Guelphen_US
dc.rights.licenseAll items in the Atrium are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectelectronic structureen_US
dc.subjectbase-free organolithium compoundsen_US
dc.subjectnuclear magnetic resonance spectroscopyen_US
dc.subject'ab initio' calculationsen_US
dc.titleSolid-state NMR spectroscopy and ab initio calculations of some base-free organolithium compoundsen_US
dc.typeThesisen_US

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