Aggregation of [Au(CN)4]- anions: Examination by crystallography and 15N CP-MAS NMR and the structural factors influencing intermolecular Au⋯N interactions

To investigate the factors influencing the formation of intermolecular Au···NC interactions between [Au(CN)4]− units, a series of [cation]n+[Au(CN)4]n double salts was synthesized, structurally characterized and probed by IR and 15N{1H} CP-MAS NMR spectroscopy. Thus, [nBu4N][Au(CN)4], [AsPh4][Au(CN)4], [N(PPh3)2][Au(CN)4], [Co(1,10-phenanthroline)3][Au(CN)4]2, and [Mn(2,2′;6′,2′′-terpyridine)2][Au(CN)4]2 show [Au(CN)4]− anions that are well-separated from one another; no Au−Au or Au···NC interactions are present. trans-[Co(1,2-diaminoethane)2Cl2][Au(CN)4] forms a supramolecular structure, where trans-[Co(en)2Cl2]+ and [Au(CN)4]− ions are found in separate layers connected by Au−CN···H−N hydrogen-bonding; weak Au···NC coordinate bonds complete octahedral Au(III) centers, and support a 2-D (4,4) network motif of [Au(CN)4]−-units. A similar structure-type is formed by [Co(NH3)6][Au(CN)4]3·(H2O)4. In [Ni(1,2-diaminoethane)3][Au(CN)4]2, intermolecular Au···NC interactions facilitate formation of 1-D chains of ...