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Mixed anion lithium complexes : models for superbases

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Lockhart-Gillett, Bryce James (2011) Mixed anion lithium complexes : models for superbases. PhD thesis, University of Tasmania.

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Abstract

The work reported in this thesis describes the synthesis, characterisation, and
reactivity of several mixed anion lithium complexes.
Chapter 2 is concerned with the design, synthesis, and characterisation of the mixed
phenol/amine containing ligands, which serve as the backbone for mixed O/N anion
lithium complexes also described. N-phenylsalicylaldamine, (ONPhH2),
N-2,6-diisopropylsalicylaldamine (ONDIPPH2), and N-t-butylsalicylaldamine
(ONtBuPhH2), were prepared from their corresponding imine precursors, which were
themselves prepared via imine condensation of the appropriate primary amines with
salicylaldehyde. Solid state structures were obtained for the amine compounds,
which display intermolecular H-bonding networks.
Chapter 2 also details the synthesis, and characterisation of mono- and some
dilithiated complexes of the O/N ligands. The monolithiated complexes were
observed to exclusively form tetrameric species. The two complexes
[ {Li(ONPhH)}4] and [ {Li(ONDIPPH)}4] were prepared by lithiation of the
corresponding amine ligands with n-BuLi in 40-60 °C petroleum spirits. The
dilithiated complexes were observed to preferentially form dimers in the solid state.
Two dimeric dilithiated complexes [ {Li2(ONPh) }2(THF)6] and
[ {Li2(ONDIPP) }2(THF)4] were prepared by lithiation of the amine ligands with
n-BuLi in THF. Several of the lithiated complexes underwent various solvent
exchange reactions yielding related complexes; the THF solvated monolithiated
tetrameric complex [ {Li(ONPhH)}4(THF)3] was obtained by exposing
[ {Li(ONPhH)}4] to THF, and the dilithiated complexes [ {Li(ONPh)}2(TMEDA)3],
[ {Li2(ONDIPP)}2(TMEDA)2], [ {Li(ONPh) }2(DME)2(THF)2], and
[ {Lh(ONDIPP) }2(DME)2] were prepared by exposing the dilithiated THF complexes
to TMEDA and DME respectively.
(TMEDA = N,N,N',N'-tetramethylethylenediamine, DME = 1,2-dimethoxyethane). A
related tetrameric dilithiated complex [ {Li2(ONPh)}4(THF)4] was obtained from
[ {Li2(ONPh) }2(THF)6] by heating in benzene.
Chapter 3 describes further solvent exchanged dilithiated complexes. ...This chapter also describes the reactivity of some of the dilithiated complexes towards ether type substrates. Cleavage of both aliphatic and
aromatic ether molecules was observed, with predictable stereospecificity correlated
to the observed geometry of the dilithiated complex. From this reactivity a further
monolithiated complex containing a modified N-methylated ligand was obtained [ {Li(ON(Me)PhH)}4].
Chapter 4 reports the synthesis and characterisation of mixed amide/alkoxide ligands
and their complexes. ...
Chapter 5 is a compilation of some serendipitous compounds that were isolated from
reactions described in Chapter 2 and Chapter 3. ... Some theoretical work was undertaken to investigate the preference of the dimeric complexes in Chapter 2 towards particular core geometries observed in the solid
state. In addition, a possible reaction pathway for the cleavage of DME was modelled
in Chapter 3, and supports the observed stereospecificity of the reaction.

Item Type: Thesis (PhD)
Copyright Holders: The Author
Copyright Information:

Copyright 2011 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
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Additional Information:

Available for use in the Library and copying in accordance with the Copyright Act 1968, as amended. Thesis (PhD)--University of Tasmania, 2011. Includes bibliographical references

Date Deposited: 19 Dec 2014 02:56
Last Modified: 17 Jul 2017 07:02
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