A dinuclear Pt–Au complex showing an unusual metal-metal bonding situation: A snapshot of a transmetalation process

The dinuclear Pt-Au complex [(CNC)(PPh3)PtAu(PPh3)](ClO4) (2) (CNC = 2,6-diphenylpyridinate) has been prepared. Its crystal structure shows a rare metal-metal bonding situation, with very short Pt–Au and Au-Cipso(CNC) distances and dissimilar Pt-Cipso(CNC) bonds. Multinuclear NMR spectra of 2 show the persistence of the Pt–Au bond in solution and the operation of an unusual fluxional behavior involving the [Pt] and [Au] metal fragments. The [Pt]···[Au] interaction has been thoroughly studied by means of DFT calculations. The observed bonding situation in 2 can be regarded as a model for an intermediate in a transmetalation process. The study of complexes containing intermetallic interactions between closed or pseudo-closed shell transitions metals (d, d, ds) is a field which is attracting a considerable attention in chemistry. These interactions have proven to be a powerful tool for crystal engineering, and the complexes containing them show interesting photophysical and photochemical properties related to the occurrence of M–M bonds. 7] Besides, the interest on these systems has increased lately because species containing this kind of interactions play a central role in cooperative catalysis. For example, complexes with Pt–Au, Pt–Cu or Pt–Ag bonds have been identified in either gas phase or in solution as intermediates in transmetalation reactions involving methyl groups, whereas Pd–Au or Pd–Cu species have been proposed as transition states in aryl ligand interchange processes. 13] However, scarce experimental evidences supporting this