Inner-sphere versus outer-sphere coordination of BF4- in a NHC-gold(I) complex

Richard M. P. Veenboer, Alba Collado, Stephanie Dupuy, Tomas Lebl, Laura Falivene, Luigi Cavallo, David B. Cordes, Alexandra M. Z. Slawin, Catherine S. J. Cazin, Steven P. Nolan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)
2 Downloads (Pure)

Abstract

The role of counterions in chemistry mediated by gold complexes stretches much further than merely providing charge balance to cationic gold species. Interplay between their basicities and coordination strengths influences interactions with both the gold center and substrates in catalysis. Actual monogold-(I) active species are generally believed to be monocoordinated species, formed from the abstraction or the decoordination of a second ligand from precursor complexes, but only a small amount of experimental evidence exists to underpin the existence of these transient species. The formation of a bench-stable neutral IPrCI-gold(I) tetrafluoroborate complex is reported herein. Experimental studies by X-ray diffraction analysis and NMR spectroscopy and theoretical studies by DFT calculations were conducted to determine the composition, structure, and behavior of this complex. The absence of an auxiliary ligand resulted in inner-sphere coordination of the counterion in the solid state. In solution, an equilibrium between two conformations was found with the counterion occupying inner-sphere and outer-sphere positions, respectively. Stoichiometric and catalytic reactivity studies with the tetrafluoroborate complex have been conducted. These confirmed the lability of the inner-sphere coordinating counterion that gives the IPrCI-gold(I) fragment behavior similar to that of related systems.

Original languageEnglish
Pages (from-to)2861-2869
Number of pages9
JournalOrganometallics
Volume36
Issue number15
Early online date20 Jul 2017
DOIs
Publication statusPublished - 14 Aug 2017

Keywords

  • N-heterocyclic carbene
  • Silver-free protocols
  • Gold catalysis
  • Gold(III) complexes
  • Reaction-mechanism
  • Highly efficient
  • Stereoselective hydrocarboxylation
  • Alkynes
  • Counterion
  • NHC

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