“Silver Effect” in Gold(I) Catalysis: An Overlooked Important Factor

Clear experimental evidence from X-ray photoelectron
spectroscopy
and 31P NMR spectroscopy has been obtained for the first
time to confirm that the combination of Ag+ cation with
[L-Au]+ results in the formation of different complexes
in solution. Re-evaluation of literature-reported gold-catalyzed reactions
revealed a significant difference in the reactivities with and without
silver. In extreme cases (more than “rare”), the conventional
[L-Au]+ catalysts could not promote the reaction without
the presence of silver. This investigation has therefore revealed
a long-overlooked “silver effect” in gold catalysis
and should lead to revision of the actual mechanism.