Cadmium Dicyanoaurates and Their Reaction with Ammonia.

The synthesis and crystal structures of two anionic cadmium dicyanoaurate coordination polymers, [ n Bu 4 N] 6 [(Cd 4 Cl 4 ) 2 (Au(CN) 2 ) 12 ][CdCl 4 ] (TCCA) and [ n Bu 4 N] 2 [Cd(Au(CN) 2 ) 4 ], and their reaction with ammonia vapour is reported. TCCA and the isostructural [ n Bu 4 N] 6 [(Cd 4 Br 4 ) 2 (Au(CN) 2 ) 12 ][CdBr 4 ] form 3-D arrays with [Cd 4 X 4 ] 4+ (X=Cl, Br) cubane clusters linked from each octahedral Cd(II) centre by three bridging [Au(CN) 2 ] - units. TCCA reacts with ammonia with concentrations of 1000 ppm or higher to give a product with a quantum yield of 0.88, while [ n Bu 4 N] 2 [Cd(Au(CN) 2 ) 4 ], which forms a 2-D anionic Cd[Au(CN) 2 ] 2 sheet structure with axially pendant [Au(CN) 2 ] - units, reacts with concentrated ammonia vapour to generate Cd(NH 3 ) 2 [Au(CN) 2 ] 2 ; this has a similar 2-D sheet structure but with axial NH 3 units. Vibrational spectroscopy illustrated that the reaction of both Cd/[Au(CN) 2 ]-based materials with ammonia proceeded by breaking Cd-NC bonds. For [ n Bu 4 N] 2 [Cd(Au(CN) 2 ) 4 ], this results in decomposition into [ n Bu 4 N][Au(CN) 2 ] ⋅ 0.5H 2 O and Cd(NH 3 ) 2 [Au(CN) 2 ] 2 , while the reaction of ammonia with TCCA is reversible by heating the ammonia-bound sample above 110 °C. Cd[Au(CN) 2 ] 2 can be prepared by thermal removal of NH 3 units from Cd(NH 3 ) 2 [Au(CN) 2 ] 2 .