Metal–betaine interactions. Part 3. Crystal structures of polymeric diaquabis(betaine)disilver(I) dinitrate and bis(pyridine betaine)disilver(I) diperchlorate

Abstract

Two polymeric silver(I) complexes of betaine (Me₃⁺NCH₂CO₂^–, L¹) and pyridine betaine (C₅H₅-⁺NCH₂CO₂^–, L²) have been prepared and characterized by X-ray Crystallography. The complexes [{Ag₂L¹₂(H₂O)₂(NO₃)₂}_n]1 and [{Ag₂L²₂(ClO₄)₂}_n]2 are structurally similar, being composed of centrosymmetric carboxylato-bridged Ag₂(carboxylato-O,O′)₂ dimers (Ag–O 2.21–2.41 Å) which are extended into a ‘stairs-like’ polymer through the co-ordination of each metal centre by a carboxylate oxygen atom [Ag–O 2.47–2.50 Å] from an adjacent dimer. In addition, the primary co-ordinating sphere about the silver atom is completed by an aqua ligand [Ag–O 2.554(3)Å] in complex 1 and by a perchlorate oxygen atom [Ag–O 2.415(3)Å] in 2. The intra-dimer Ag ⋯ Ag distance is 2.898(1) for 1 and 2.814(2)Å for 2, the latter being one of the shortest among known dinuclear silver(I) carboxylates.