Synthesis and structures of carboxylate-bridged polynuclear copper(II)–lanthanide(III) complexes [CuLn(C5H5N+CH2CO2–)5(H2O)5][ClO4]5·2H2O (Ln = La or Nd) and [Cu3Nd2(C5H5N+CH2CO2–)10(NO3)2(H2O)8][ClO4]10·4H2O

Abstract

Two types of carboxylate-bridged copper(II)–lanthanide(III) complexes, [CuLn(C₅H₅N⁺CH₂CO₂^–)₅(H₂O)₅][ClO₄]₅· 2H₂O 1 (Ln^III = La^III a or Nd^III b) and [Cu₃Nd₂(C₅H₅N⁺CH₂CO₂^–)₁₀(NO₃)₂(H₂O)₈][ClO₄]₁₀·4H₂O 2, have been synthesized and characterized by X-ray structural analysis. Complexes 1a and 1b are isomorphous. In both, a Cu^II atom is quadruply bridged to a Ln^III atom by four µ-carboxylate groups at the basal positions, and co-ordinated by an aqua ligand at the apical position to form a square-pyramidal CuO₄(OH₂) geometry, while the Ln^III atom is co-ordinated in a monocapped square antiprism by five carboxy oxygen atoms and four aqua ligands. In 2, a pair of Cu^II atoms in two centrosymmetrically related tetrakis(µ-carboxylate)-bridged dinuclear Cu^IINd^III subunits is each linked to the central Cu^II atom by a single syn-antiµ-carboxylate bridge, resulting in a pentanuclear cation. The central Cu^II atom is co-ordinated by two carboxy oxygen atoms and two aqua ligands in a distorted square-planar fashion; the other two Cu^II atoms adopt the same square-pyramidal geometry, each being ligated by the four oxygen atoms from the quadruple carboxylate bridges at the basal plane and by one oxygen atom of the syn-antiµ-carboxylate group at the apical position. The Nd^III atom is co-ordinated in a distorted monocapped square antiprism by the four carboxy oxygen atoms, three aqua ligands and a chelate nitrate group.