Water Displacement by Cyanogold Complexes in Binuclear Nickel(II) Compounds Based on Bridging Oxalate. Synthesis, Structural Diversity, Magnetic Properties, and DFT Calculations

Several cyanogold complexes react with the binuclear nickel complex [{Ni(dien)(H2O)}2(μ-ox)](PF6)2·2H2O to give
the compounds [{Ni(dien)(H2O)}2(μ-ox)]Br2 (1), [{Ni(dien)(Au(CN)2)}2(μ-ox)] (2), and [{Ni(dien)}2(μ-ox){μ-Au(CN)4}](PF6) (3) (dien, diethilenetriamine; ox, oxalate). In the case of compounds 2 and 3, water displacement by
the corresponding cyanogold complex takes place, whereas compound 1 is formed by a substitution of the anion.
The crystal structures of compounds 1 and 2 present a 2D arrangement where the layers are connected by van
der Waals forces (1) or N−H···N⋮C hydrogen bonds (2), where each binuclear complex is hydrogen bonded to
its neighbors, whereas compound 3 presents a novel structure where the tetracyanoaurate acts as a bridging
ligand to give a polymeric compound. Magnetic studies of these compounds reveal an antiferromagnetic behavior.
Finally, density functional theory (DFT) calculations have been performed on isolated models of compounds 2 and
3 in order to gain some insight about the different behavior of the [Au(CN)2]- and [Au(CN)4]- groups as ligands
and proton acceptors in hydrogen bonds.