The water-soluble carbene ligand precursors sIMesH+Cl - and sSIMesH+Cl- were synthesized in high yields by direct sulfonation of IMesH+Cl- (1,3-bis(2,4,6-trimethylphenyl) imidazolium chloride) and SIMesH +Cl- (1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride). Gold(I)-N-heterocyclic carbene complexes [AuCl(sIMes)] and [AuCl(sSIMes)] were prepared by carbene transfer from the zwitterionic [Ag(sIMes)2] and [Ag(sSIMes)2] to [AuCl(tht)] (tht = tetrahydrothiophene). In methanol-water mixtures or in neat water, the new gold(I)-NHC complexes showed high catalytic activity in Markovnikov type hydration of terminal alkynes (up to a turnover frequency 1990 h-1; ethynyltoluene, 0.1 mol% catalyst) but were markedly less active in case of internal alkynes (TOF = 3.6 h-1; diphenylethyne, 1 mol% catalyst). These new Au(I)-NHC catalysts do not require acid co-catalysts or activation by Ag(I)-additives.
- Gold(I)-NHC complexes
- Water-soluble catalysts
ASJC Scopus subject areas
- Process Chemistry and Technology
- Physical and Theoretical Chemistry