A 2D grid-shaped cyanide-bridged Co(II)-Au(I) bimetallic coordination polymer, [Co(DMF) 2 {Au(CN) 2 } 2 ], has been prepared from the [Au(CN) 2 ] 2 building block; sheets associate pair-wise by aurophilic interactions and the compound exhibits zeolite-like properties. Cyanide-bridged bimetallic systems, prepared from assembling cyanometallates and transition metal complexes building blocks, have been shown to exhibit fascinating structures with interesting magnetic, electrochemical,

more »

... cal and zeolitic properties. 1 Linear cyanometallates, [M(CN) 2 ] 2 (M = Ag(I) and Au(I)), however, have been infrequently used as building blocks, probably as a consequence of their diamagnetic nature. Interestingly, gold(I) atoms of dicyanoaurate groups may be involved in intermolecular interactions comparable to hydrogen bonds. This closed-shell intermolecular interaction between gold(I) atoms, sometimes called aurophilicity, is known to be an useful tool for the design of intriguing and interesting polymeric structures in solid state. 2 Therefore, the interplay between covalent and aurophilic interactions involving dicyanoaurate groups might produce novel structural topologies. Moreover, according to precise theoretical calculations, the Au-Au interaction is effective over a wide range of distances. 3 In a earlier statistical study 4 based on 693 goldcontaining structures, it was found that there exists a strong correlation between the Au-Au distance (in the range 3-4 Å) and the dihedral angle between the donor atoms attached to the two adjacent gold atoms: the shorter the Au-Au distance is, the higher will be the probability of the staggered conformation. This has been also observed for dicyanoaurate containing compounds. 5 An interesting cation used in synthetic work with dicyanoaurate(I) anions is the cobalt(II) cation with its ability to display either octahedral or tetrahedral coordination. 6 For both chromophores the resulting structure in the solid state is a threedimensional network, where both ends of the dicyanoaurate(I) anions are coordinated to a cobalt(II) cation. Interestingly, the shortest Au-Au distances are significantly different: 3.11 Å in the tetrahedral and 3.33 Å in the octahedral analogue. If some of the coordination sites of a cation are blocked by an additional ligand, the dimensionality can be varied and then it might be possible to analyse the influence of the aurophilic interactions on the final structure. For instance, in a formally 1D structure of (tmeda)Cu[Au(CN) 2 ] 2 (tmeda = N,N,NA,NA-tetramethylethylenediamine) 7 the aurophilicity enhances the dimensionality to 3D, with Au-Au distances of 3.345 and 3.538 Å, less than the sum of the van der Waals radii of Au (3.60 Å). Here we applied the same strategy in synthetic work. 8 From the reaction of K[Au(CN) 2 ] and Co(Ac) 2 ·4H 2 O in DMF the bimetallic assembled compound [Co(DMF) 2 {Au(CN) 2 } 2 ] (1) was obtained as pink crystals. The crystal structure of 1 9 consists of parallel sheets lying in bc-plane, made up of edgesharing approximate square-planar {NC-Au-CN-Co} 4 units C H E M . C O M M U N . , 2 0 0 2 , 5 9 2 -5 9 3