Thesis

Advances in synthetic, structural and reaction chemistry of zinc and zincate complexes containing alkyl and/or amido ligands

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Awarding institution
  • University of Strathclyde
Date of award
  • 2014
Thesis identifier
  • T13693
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Department, School or Faculty
Abstract
  • One of the most important reactions in chemistry, metallation benefits society in general as it is utilised for the synthesis of many commodities used in daily life. While lithium-based monometallic compounds have long been the reagents of choice for metallation, bimetallic reagents are emerging as second generation metallating agents that can overcome many limitations of lithium reagents. This study extends "synergic" bimetallic chemistry focusing mainly on sodium, zinc and sodium zincate systems, investigating their syntheses, structures and reactions with organic substrates. Probing the metallation of trifluoromethylbenzene, using tBuLi or nBuNa activated by a donor (THF, TMEDA or PMDETA), established the metallation system dictated both regioselectivity and yield. The origin of the increased ortho-selectivity using sodium systems was uncovered through analysis of isolated metallated intermediates [(TMEDA)·Li(C6H4-CF3)]2, 3, [(TMEDA)·Na(C6H4-CF3)]2, 4 and [(PMDETA)·Na(C6H4-CF3)]2, 5. Since pyrrole is important within pharmaceuticals and zinc-pyrrole chemistry is remarkably underdeveloped, we have synthesised the first crystallographicallycharacterized zinc pyrrolyl complexes, with one, two, three or four pyrrole anions attached to zinc in [tBuZn(NC4H4)(TMEDA)·HNC4H4], 7; [Zn(NC4H4)2(TMEDA)], 8; [{(THF)2·NaZn(THF)(NC4H4)3}∞], 9; [{(TMEDA)·Na}2Zn(NC4H4)4], 10; [{(PMDETA)·Na}2Zn(NC4H4)4], 11, as well as for comparison [{(PMDETA)·Na(NC4H4)}2], 12. Improving upon sub-ambient temperature protocols, ambient temperature zincation of N-Boc pyrrolidine was achieved via sodium zincate [(TMEDA)Na(μ-TMP)(μ-tBu)Zn(tBu)]. Metallated intermediate [(TMEDA)Na(TMP)(α-NC4H7NBoc)Zn(tBu)] 13 was crystallographically characterised. Exploring the basicity of 13, in situ sidereactions with toluene, ferrocene or anisole generated [{(TMEDA)Na[OC(NC4H8)CHPh]}2], 14, [(TMEDA)(Boc-NC4H8)Na{(η2-C5H4)Fe(C5H5)}Zn(tBu)2], 16 and [(TMEDA)Na(μ-TMP)(μ-C6H4OMe)Zn(tBu)], 17, respectively. Incorporating multifunctional 2,2'-dipyridylamide (dpa) into a bimetallic system produced neutral zinc, sodium and potassium zincates with unprecedented structures in [{(dpa)Zn(tBu)}2]; 18, [(TMEDA)2Na2(μ-dpa)2Zn(tBu)2]; 19, [{Na(THF)6}+{Zn(tBu)2(dpa)Zn(tBu)2}-]; 20, [{K(THF)6}+{Zn(tBu)2(dpa)Zn(tBu)2}-], 21. Sodium zincates 19 and 20 tert-butylate benzophenone at the challenging para-position, whereas di-tert-butylzinc failed to react. Another difunctional amide, N'-benzyl-N,N-dimethylethylenediamide (BD) generated sodium zincate [(TMEDA)Na(μ-BD)(μ-tBu)Zn(tBu)], 25, which successfully deproto-metallated both N,N-diisopropylbenzamide and anisole.
Advisor / supervisor
  • Mulvey, Robert
Resource Type
DOI
Date Created
  • 2014
Former identifier
  • 1028953

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