Thesis

New amides, amidinides and mixed-metal derivatives thereof in magnesium chemistry

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Awarding institution
  • University of Strathclyde
Date of award
  • 1998
Thesis identifier
  • T9534
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Abstract
  • Research has been directed towards the development of organonitrogen-magnesium chemistry, focusing on amide ligands mainly, and on amidinide ligands to a lesser extent. New compounds have been characterised by elemental analyses and NMR spectroscopic studies and seventeen of them have been crystallographically authenticated by X-ray diffraction. Within the area of dianionic ligands, it has been found that deprotonating 1,8-diaminonaphthalene twice with dibutylmagnesium leads to [{(1,8-C₁₀H₆(NH)₂)Mg.HMPA}₃.2THF], the first magnesium amide trimer, having an unprecedented N₆Mg₃ cage structure. In contrast, treating the diamines N,N'diphenylethylenediamine or N,N' -dibenzylethylenediamine with the same reagent in the same stoichiometry produces [{MgN(Ph)CH₂CH₂N(Ph).2THF(1.5THF)}₂], [{MgN(CH₂Ph)CH₂CH₂N(CH₂Ph).HMPA}₂], or [MgN(Ph)CH₂CH₂N(Ph).2HMPA], which adopt more conventional dimeric ring or monomeric structures. Also, the novel magnesium aluminate salt, [Mg(HMPA)₄.2AlMe₄], has been synthesised serendipitously from an attempt to make a mixed-metal diamide complex. Within the area of monoanionic ligands, two structurally related mixed lithium-magnesium amides, [{(Me₃Si)₂N}₁₃LiMg] and [{(c-C₆H₁₁)₂N}₃LiMg.THF], based on discrete (NLiNMg) cyclic cores, have been prepared. Further exploration of the hexamethyldisilazide has opened up a remarkable new area of macrocyclic chemistry. Thus, magnesium-substituted derivatives of classical alkali metal amide ring structures, [{(Me₃Si)₂N}₄Li₂Mg₂(0₂)x(O)y] and [{(Me₃Si)₂N}₄Na₂Mg₂(0₂)x(O)y], having oxo or peroxo core dianions for charge balance, have been established. The tetramethylpiperidide analogue, [{Me₂CCH₂CH₂CH₂(Me)₂CN}₄Li₂Mg₂(O)], has also been made. In an extension of this work, a larger twelve-membered (N₆Na₄Mg₂)²⁺ cationic ring system have been realised through [{Me₂C(CH₂)₃(Me)₂CN}₆Na₄Mg₂{C₆H₃(CH₃)}] and [{Me₂C(CH₂)₃(Me)₂CN}₆}Na₄Mg₂(C₆H₄)}]. This ring acts as a templating host for the selective di-deprotonation of toluene and benzene respectively, the dianions of which occupy the ring centre. Possible insight into the mechanism of arene incorporation in these macro cycles is gained through the structure of [{(Me₃Si)₂N}₆K₂Mg₂.4{C₆H₅(CH₃)}], the first potassium amido magnesate species. Finally, two magnesium and one lithium-magnesium amidinide structures, [{PhNC(Ph)NPh}₂Mg.2DMSO,C₆H₅CH₃] [{PhNC(Ph)NPh}₂Mg.2HMPA,C₆H₅CH₃] and [{PhC(NSiMe₃)₂}₄Li₄Mg(O)] respectively, have been reported.
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DOI
EThOS ID
  • uk.bl.ethos.674847
Date Created
  • 1998
Former identifier
  • 556475

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