Targeting [AuCl2(CN)2]− units as halophilic building blocks in coordination polymers

Several new [AuCl2(CN)2]−-containing complexes were synthesized with a range of ancillary ligands and first row transition metals. Use of Cu(II) and 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (Me2phen) with [nBu4N][AuCl2(CN)2] yielded the ionic compounds [Cu(phen)2(OHMe)][AuCl2(CN)2]2 (1) and {Cu(Me2phen)2[AuCl2(CN)2]}[AuCl2(CN)2] (2). Use of 2 , 2 ′ ; 6 ′ , 2 ″ -terpyridine (terpy) and Cu(NO3)2·3H2O or Cu(ClO4)2·6H2O instead yielded Cu(terpy)[AuCl2(CN)2]2 (3) and Cu(terpy)( μ -ClO4)[AuCl2(CN)2] (4), respectively. Compound (3) is molecular, with a single terpy ligand and two pendant [AuCl2(CN)2]− units bound to a Cu(II) centre, whereas 4 is a linear 1-D coordination polymer consisting of Cu(II) centres bridged by ClO 4 - moieties. Using Cu(II) and pyrazine (pyz) generates a 1-D coordination polymer, Cu(pyz)(NCMe)2[AuCl2(CN)2]2·2MeCN (5) with bridging pyz units and pendant [AuCl2(CN)2]− and NCMe moieties. Upon switching to 4,4′-bipyridine (bipy), the 3-D coordination polymer, {Cu(bipy)2[Au(CN)2]}[AuCl2(CN)2] (6) results, which is built up of sheets of Cu(II)/bipy units bridged by [Au(CN)2]−. Free [AuCl2(CN)2]− anions sit in the network cavities, held by a rare, unsupported Au I ⋯ Au III interaction of 3.4530(10) Å. The inability of [AuCl2(CN)2]− to act as a bridging unit in any of these ancillary ligand-containing structures is consistent with the behaviour of [AuBr2(CN)2]− in previous studies and shows that [AuCl2(CN)2]− holds no advantages over [AuBr2(CN)2]− in coordination polymer formation. In the absence of ancillary ligands, molecular Mn(OH2)4[AuCl2(CN)2]2 (7) and the 1-D coordination polymer Co(OH2)4[AuCl2(CN)2]2·2H2O (8), the first coordination polymer with [AuCl2(CN)2]− as the primary bridging moiety, were also prepared and structurally characterized.