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Issue 24, 2017
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Stable AuIII complexes with four N-heterocyclic carbene groups can be prepared in high yield directly from KAuCl4

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Abstract

Gold(III) N-heterocyclic carbene (NHC) complexes of form [Au(NHC)4Cl2]Cl were synthesized by reaction of KAuCl4 with bis- and tetrakis(imidazolium) salts in the presence of a mild base. Treatment of these complexes with KPF6 afforded four-coordinate AuIII complexes of form [Au(NHC)4](PF6)3. X-Ray crystallography showed the [AuIII(NHC)4]3+ cations in the hexafluorophosphate salts to have a square planar Au(NHC)4 moiety [Au⋯CNHC 2.024(4)–2.082(7) Å]. In the [AuIII(NHC)4Cl2]+ cations in the chloride salts, coordination about Au was tetragonally-distorted octahedral, the axial Au–Cl bonds being substantially longer [Au⋯Cl 3.148(2)–3.693(1) Å] than the equatorial Au–CNHC bonds [Au⋯C 2.024(4)–2.082(7) Å]. NMR and conductance studies suggested that the structures of the complexes seen in the solid state persisted in DMSO solution, except in one case where a chlorido ligand dissociated from [AuIII(NHC)4Cl2]+ to form [AuIII(NHC)4Cl]2+. The AuIII(NHC)4 unit was surprisingly robust. An AuIII complex was found to undergo H/D exchange reactions in D2O solution at 100 °C with no signs of decomposition detectable by 1H NMR spectroscopy. 1H NMR studies showed that various complexes containing AuIII(NHC)4 moieties underwent little or no decomposition when heated at 120 °C in DMSO-d6 for extended periods.

Graphical abstract: Stable AuIII complexes with four N-heterocyclic carbene groups can be prepared in high yield directly from KAuCl4

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Publication details

The article was received on 10 Apr 2017, accepted on 01 Jun 2017 and first published on 02 Jun 2017


Article type: Paper
DOI: 10.1039/C7DT01272A
Citation: Dalton Trans., 2017,46, 7844-7856
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    Stable AuIII complexes with four N-heterocyclic carbene groups can be prepared in high yield directly from KAuCl4

    A. H. Mageed, B. W. Skelton and M. V. Baker, Dalton Trans., 2017, 46, 7844
    DOI: 10.1039/C7DT01272A

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