Identification of (phosphine)gold(I) hydrates and their equilibria in wet solutions

07 Nov 2012

Scientists from China have identified and characterised the elusive gold(I) hydrates that result from the common gold(I) pre-catalyst Ph₃PAuOTf.

Gold(I) complexes have been the subject of a great deal of attention in recent year due to their application in a broad range of chemical reactions and their excellent catalytic activity. Their advantages over some other metal catalysts includes their insensitivity to moisture, therefore not requiring a completely ‘dry’ reaction environment and instead can even be used in reactions with water as the solvent.

Amongst some of the ambiguous aspects of the catalytic species actually involved in these transformations, the exact role of water, and whether it reacts with the gold complexes, is uncertain. This is important in order to gauge the impact water has on the catalytic activity and the turnover frequency. In this work, Biao Yu and Yu Tang from the Shanghai Institute of Organic Chemistry, China, identified two gold(I) hydrates from the Ph₃PAuOTf pre-catalyst – [Ph₃PAu(OH₂)]⁺TfO⁻and [(Ph₃PAu)₂(OH)₂]²⁺(TfO⁻)₂, resulting in the disclosure of the equilibria between gold oxo species in wet solutions. The results presented here help to explain further the stability of some gold complexes in water and the instability of others.