Metallophilic interactions in silver(I) dicyanoaurate complexes

This manuscript reports four new gold(I)−silver(I) complexes with 2-(2-pyridyl)-1,8-naphthyridine (pyNP) and terpyridine (terpy) as ancillary ligands, of formulation [Ag(pyNP)(Au(CN)2)]2 (1), [Ag2Au2(μ-CN)2(CN)2(pyNP)2] (2), [Ag2Au(μ-CN)2(terpy)2][Au(CN)2] (3) and [Ag4Au4(μ-CN)8(terpy)2(py)] (4). Complexes 1 and 2 are structural isomers obtained from different solvents. The Au(CN)2- anion is not coordinated and establishes intramolecular Au···Ag,Ag interactions in 1. In contrast, it is monocoordinated to silver atoms via a CN fragment in compound 2 and no metallophilic interaction is observed. In compound 3, one Au(CN)2 anion bridges two Ag(terpy) fragments. In this complex an infinite array of gold atoms is found, exhibiting aurophilic interactions of 3.415 Å. In complex 4 the 3D architecture observed in the crystal packing is driven by Au···Au and Au···Ag metallophilic interactions. All compounds have been structurally and vibrationally characterized to better understand the crystal forces. In addition, a solution chemistry study performed in different solvents with ESI-MS spectrometry was performed to comprehend the speciation and solvent effects. Finally, DFT calculations were carried out to analyze the Ag···Au interactions and also the π-stacking interactions that are relevant in the crystal packing of some structures. Special attention has been paid to the bifurcated nature of the Au···Ag,Ag interactions in compound 1, that has been analyzed theoretically by using the quantum theory of atoms-in-molecules (QTAIM) and the Natural Bond Orbital (NBO) computational tools