Tuning main group redox chemistry through steric loading: Subvalent group 13 metal complexes of carbazolyl ligands

Hassanatu B. Mansaray, Michael Kelly, Dragoslav Vidovic, Simon Aldridge

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17 Citations (Scopus)

Abstract

The ability of substituted carbazol-9-yl systems to ligate in δ fashion through the amido N-donor, or to adopt alternative coordination modes through the π system of the central five-membered ring, can be tuned by systematic variation in the steric demands of substituents in the 1- and 8-positions. The differing affinities of the two modes of coordination for hard and soft metal centres can be shown to influence not only cation selectivity, but also the redox properties of the metal centre. Thus, the highly sterically sterically demanding 1,3,6,8-tetra-tert-butylcarbazolyl ligand can be used to generate the structurally characterised amido-indium(I) complex, [{(tBu 4carb)In}n], (together with its isostructural thallium counterpart) in which the metal centre interacts with the central pyrrolyl ring in ≠3 fashion [d(-N)=2.679(3) Å; d(-C)=2.819(3), 2.899(3) Å]. By contrast, the smaller 3,6-di-tert-butylcarbazolyl system is less able to restrict the metal centre from binding at the anionic nitrogen donor in the plane of the carbazolyl ligand (i.e. in δ fashion). Analogous chemistry with InI precursors therefore leads to disproportionation to the much harder InII [and In0], and the formation of the mixed-valence product, [In2{In2(tBu 2carb)6}], a homoleptic molecular [In4(NR 2)6] system. This chemistry reveals a flexibility of ligation for carbazolyl systems that contrasts markedly with that of the similarly sterically encumbered terphenyl ligand family. Carbazoles and indiums: The ability of substituted carbazol-9-yl systems to ligate in δ-fashion through the amido N-donor, or to adopt alternative coordination modes through the π system of the central five-membered ring, can be tuned by systematic variation in the steric demands of substituents in the 1- and 8-positions. The differing affinities of the two modes of coordination for hard and soft metal centres can be shown to influence not only cation selectivity, but also the redox properties of the metal centre (see figure).

Original languageEnglish
Pages (from-to)5381-5386
Number of pages6
JournalChemistry - A European Journal
Volume17
Issue number19
DOIs
Publication statusPublished - 2 May 2011
Externally publishedYes

Keywords

  • amides
  • Group 13 elements
  • indium
  • ligand design
  • subvalent complexes
  • thallium

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