Dimeric Gold Bis(carbene) Complexes by Transmetalation in Water

Due to its cost, environmental benefits, and safety advantages,
water has become more and more important as a solvent for catalytic
reactions and constitutes the best environment for biomedical applications.
Therefore, water-soluble and water-stable metal complexes containing
strong σ-donor ligands such as N-heterocyclic carbenes (NHCs)
are of great interest in modern coordination chemistry. In this paper
we present the successful preparation of two new dinuclear gold­(I)–bis­(NHC)
complexes in water, by applying the Ag–NHC transfer route.
This green synthetic strategy is valuable for gold­(I) compounds involving
N-functionalized neutral and dianionic bis­(NHC) ligands. These two
water-soluble compounds were analyzed by spectroscopic methods and
by X-ray diffraction. Furthermore, ab initio and DFT calculations
on the corresponding dinuclear gold complexes illustrate the important
influence of the electrostatic environment of the dinuclear entity
on the aurophilic interactions and help to understand the molecular
arrangement presented in this paper.