Metal-phenoxyalkanoic acid interactions Part 10. Crystal and molecular structures of catena-[tetraaqua(4-carboxylato-phenoxyacetato)manganese(II)], tetraaquabis(4-carboxyphenoxyacetato)nickel(II) and tetraaquabis(4-carboxyphenoxyacetato)cobalt(II)

Abstract

The crystal structures of two metal(II) complexes of 4-carboxyphenoxyacetic acid have been determined by X-ray methods. The first, catena[tetraaqua(4-carboxylato-phenoxyacetato)manganese(II), (1) forms crystals which are orthorhombic, space group Pbca, with 8 molecules in a unit cell of dimensions a = 10.356(2), b = 9.086(2), c = 25.673(8) Å. It has a polymeric structure involving both cis-related carboxylate groups and four water molecules about a slightly distorted octahedron. The mean MnO (water) distance is 2.214(7) Å, while the MnO (carboxylate) distances are 2.147(6) and 2.111(7) Å. Tetraaquabis(4-carboxyphenoxyacetato)nickel(II) (2) is triclinic, space group P₁ with one molecule in the cell, dimensions a = 4.896(2), b = 5.679(2), c = 18.403(6) Å, α = 93.75(3), β = 91.78(3), γ = 95.76(2). The centrosymmetric complex units are discrete monomers with unidentate trans-related acid ligands bonded through the phenoxy carboxylate oxygen [NiO, 2.058(3) Å]. The NiO (water) distance is 2.055(4) Å. Single crystal diffractometry and elemental analysis have been used to prove that the Co(II) (3) analogue is isomorphous and isostructural with the Ni(II) complex. The p-carboxy group of one molecule is hydrogen bonded about a centre of symmetry to another p-carboxy group.