Building two-dimensional silver(I) co-ordination polymers with dicarboxylate-like ligands: synthesis and crystal structures of polymeric complexes of silver nitrate and perchlorate with flexible double betaines

Abstract

Four novel two-dimensional silver(I) co-ordination polymers of two flexible double betaines with different quaternary ammonio side groups in the adipic acid skeleton, namely [{Ag2(L1)}n][CIO4]2n1, [{Ag2(L2)}n][CIO4]2n·2nH2O 2, [{Ag2(L1)(NO3)2}n]3 and [{Ag2(L2)(NO3)2}n]4[L1=meso-2,5-bis(trimethylammonio)adipate, –O2CCH(N+Me3)CH2CH2CH(N+Me3)CO2–; L2=meso-2,5-bis(pyridinio)adipate, –O2CCH(N+C5H5)CH2CH2CH(N+C5H5)CO2–], have been prepared and characterized by X-ray crystallography. Each complex contains dimeric subunits in which each pair of adjacent metal atoms is doubly bridged by coplanar syn-synµ-carboxylato-O,O′ groups. The dimeric subunits are extended into a step polymer through the linkage of each metal centre to a carboxylate group of an adjacent dimer. Such [Ag2(carboxylate-O,O′)2]n chains are extended into sawtooth-wave layer structures in 1, 3 and 4, and an unusual corrugated layer in 2 by the cross-linkage of the adipic acid skeleton of the double-betaine ligands. The different ligation ability of the perchlorate and nitrate anions results in different co-ordination geometries about the silver(I) atoms. In 1 and 2, the silver(I) atom is co-ordinated by three carboxylato oxygen atoms in a T-shaped geometry, and the [Ag2(carboxylate-O,O′)2]n chain exhibits the typical type D structure. The co-ordination geometry of the silver(I) atom in 3 is a distorted tetrahedron, and the [Ag2(carboxylate-O,O′)2]n chain adopts a modified type D structure. The silver(I) atom in 4 exhibits unusual five-co-ordination in a square pyramid, and the dimer is converted into a novel paddlewheel-like structure, which is the first example found in silver(I) carboxylates.