Polynuclear Architectures with Di- and Tricarbene Ligands

The 1,3,5-triimidazolium-substituted benzene cation in H3-1(PF6)3 reacts with Hg(OAc)2 to yield the cylinder-like trinuclear hexacarbene complex [Hg3(1)2](PF6)6. Reaction of imidazole with 1,4-dibromobenzene gives 1,4-bis(1-imidazolyl)benzene (2), which after dialkylation with ethyl bromide and salt metathesis yields the new diimidazolium salt H2-3(PF6)2. Two equivalents of H2-3(PF6)2 react with 2 equiv of Ag2O to give the dinuclear AgI tetracarbene complex [Ag2(3)2](PF6)2, which after transmetalation with [AuCl(SMe2)] yields the AuI tetracarbene complex [Au2(3)2](PF6)2. In contrast to the formation of the tetracarbene complexes of type [M2(3)2]2+ (M = AgI, AuI), the diimidazolium salt H2-3(PF6)2 reacts with Hg(OAc)2 to yield the dinuclear HgII dicarbene complex [Hg2(OAc)2(3)](PF6)2, where each mercury center is coordinated by one carbene carbon atom and one acetate oxygen atom. The crystal structure of [Hg2(OAc)2(3)](PF6)2 reveals that the complex forms a coordination polymer via intra- and intermolecular acetate bridges between HgII centers.