Synthesis and structures of polymeric silver and mercury complexes with amido-functionalized N-heterocyclic carbenes

Four amido-functionalized N-heterocyclic silver(I) and mercury(II) carbene complexes, [(CH3-imy-CH2CONH2)2Ag2Br2] (3), [Ag(CH3-bimy-CH2CONH2)2]4[Ag4Br8] (4), [Hg(CH3-imy-CH2CONH2)2][HgBr4] (5), and [Hg(CH3-bimy-CH2CONH2)2][HgBr4] (6), have been synthesized and structurally characterized. Crystal packing revealed a 2D polymeric structure of complex 3. In addition to a repeated interaction between the Ag2Br2 units responsible for the 1D polymeric ladder structure, a pair of hydrogen bonding interactions between the amido groups of the adjacent molecules provided a basis for the other dimension of the polymeric chain. Complex 4 is comprised of a unique oligomeric anion [Ag4Br8]4− and four [Ag(CH3-bimy-CH2CONH2)2]+ cations. Crystal packing of 4 revealed a one-dimensional polymeric structure in which the cations are connected to each other through a pair of hydrogen bonding interactions between the adjacent amido groups. Compounds 5 and 6 are both ionic consisting of a mercury carbene cation and [HgBr4]2− anion. An intramolecular interaction of the amido oxygen with the mercury atom of the cation was observed in these two complexes. The interaction between the mercury of the cation and a bromide of the anion, along with the hydrogen bonding interaction of the adjacent amido groups, is responsible for the 2D polymeric structures of these two complexes in the solid state.