Mixed-Metal Triangular Trinuclear Complexes: Dimers of Gold-Silver Mixed-Metal Complexes from Gold(I) Carbeniates and Silver(I) 3,5-Diphenylpyrazolates.

Heterobimetallic molecular species can produce unique optical, catalytic, and electronic properties. For example, gold-silver clusters have been synthesized and found to be highly efficient optical materials which possess enhanced Non-Linear Optical activity (NLO) over that of the pure silver and gold complexes. This paper describes a successful approach to the synthesis of organic solvent soluble mixed-metal gold-silver compounds with 2:1 and 1:2 Au:Ag ratios. Trinuclear mixed-metal gold-silver compounds are obtained by the reaction of gold(I) carbeniate [Au(μ-C(OEt)=NC6H4-p-CH3)]3, TR(carb), with silver(I) pyrazolate [Ag(μ-3,5-Ph2pz)]3. The crystalline products are mixed-ligand, mixed-metal dimeric products [Au(carb)Ag2(μ-3,5-Ph2pz)2], [Au2(carb)2Ag(μ-3,5-Ph2pz)]•CH2Cl2. They have been characterized by elemental analysis and 1H NMR and mass spectrometry. The X-ray structure of [Au(carb)Ag2(μ-3,5-Ph2pz)2] shows it to be a dimer with two Ag•••Au contacts between the trinuclear units of 3.083(2) and 3.310(2) Å and with average intramolecular Ag•••Ag and Au•••Ag distances of ~ 3.3 and 3.2 Å, respectively. The structure of [Au2(carb)2Ag(μ-3,5-Ph2pz)]•CH2Cl2 is a dimer with one intermolecular Au•••Au attraction of 3.3354(10) Å and a short Ag•••Au distance of ~3.42 Å and intramolecular Ag•••Au and Au•••Au contacts of ~3.2 and ~ 3.3 Å, respectively. Packing diagrams of both complexes show that the dimeric units are independent, similar to their parent molecules. The white powders of these mixed-metal gold-silver compounds show a strong green luminescence under UV excitation at room temperature and a yellow luminescence at 77 K, a luminescence thermochromism.