Cadmium Dicyanoaurates and Their Reaction with Ammonia.

The synthesis and crystal structures of two anionic cadmium dicyanoaurate coordination polymers, [BuN][(CdCl)(Au(CN))][CdCl] (TCCA) and [BuN][Cd(Au(CN))], and their reaction with ammonia vapour is reported. TCCA and the isostructural [BuN][(CdBr)(Au(CN))][CdBr] form 3-D arrays with [CdX] (X=Cl, Br) cubane clusters linked from each octahedral Cd(II) centre by three bridging [Au(CN)] units. TCCA reacts with ammonia with concentrations of 1000 ppm or higher to give a product with a quantum yield of 0.88, while [BuN][Cd(Au(CN))], which forms a 2-D anionic Cd[Au(CN)] sheet structure with axially pendant [Au(CN)] units, reacts with concentrated ammonia vapour to generate Cd(NH)[Au(CN)]; this has a similar 2-D sheet structure but with axial NH units. Vibrational spectroscopy illustrated that the reaction of both Cd/[Au(CN)]-based materials with ammonia proceeded by breaking Cd-NC bonds. For [BuN][Cd(Au(CN))], this results in decomposition into [BuN][Au(CN)] ⋅ 0.5HO and Cd(NH)[Au(CN)], while the reaction of ammonia with TCCA is reversible by heating the ammonia-bound sample above 110 °C. Cd[Au(CN)] can be prepared by thermal removal of NH units from Cd(NH)[Au(CN)].