Metal–betaine interactions. Part 13. Preparation and crystal structures of four polymeric silver(I) complexes of betaine derivatives

Abstract

Four polymeric silver(I) complexes of the betaine derivatives pyridiniopropionate (C₅H₅N⁺CH₂CH₂CO₂^–, L¹) and trimethylammoniopropionate (Me₃N⁺CH₂CH₂CO₂^–, L²) have been prepared and characterized by X-ray crystallography. The complexes [(Ag₂L¹₂)_n][ClO₄]_2n1, [{Ag₂L¹₂(NO₃)₂}_n]2, [{Ag₂L²₂(NO₃)₂}_n]3 and [{Ag₂L²₂(H₂O)}_n][ClO₄]_2n·nH₂O 4 all contain bis(carboxylate)-bridged Ag₂ dimer units [Ag–O 2.185(2)–2.264(6), Ag ⋯ Ag 2.800(2)–2.901(2)Å] which are extended into stairs-like chains via the co-ordination of each metal centre by a carboxylato oxygen atom [Ag–O 2.479(4)–2.588(5)Å] from an adjacent unit. A pair of unidentate nitrate ligands occupy axial co-ordination sites on the same side and on opposite sides of the mean plane of the dimer in 2 and 3, respectively; the dimer in 4 has only one axial site occupied by an aqua ligand, resulting in uncommon inter-chain metal–metal contacts in the crystal [3.269(2) and 3.346(2)Å].