Synthesis and crystal structure of diaqua(1,4,8,11-tetraazacyclotetradecane)zinc(II) bis(hydrogen 4-phosphonatobiphenyl-4′-carboxylato)(1,4,8,11-tetraazacyclotetradecane)zinc(II)

Abstract

In the asymmetric unit of the title compound, trans-diaqua(1,4,8,11-tetraazacyclotetradecane-κ4 N 1,N 4,N 8,N 11)zinc(II) trans-bis(hydrogen 4-phosphonatobiphenyl-4′-carboxylato-κO)(1,4,8,11-tetraazacyclotetradecane-κ4 N 1,N 4,N 8,N 11)zinc(II), [Zn(C10H24N4)(H2O)2][Zn(C13H9O5P)2(C10H24N4)], both Zn atoms lie on crystallographic inversion centres and the atoms of the macrocycle in the cation are disordered over two sets of sites. In both macrocyclic units, the metal ions possess a tetragonally elongated ZnN4O2 octahedral environment formed by the four secondary N atoms of the macrocyclic ligand in the equatorial plane and the two trans O atoms of the water molecules or anions in the axial positions, with the macrocyclic ligands adopting the most energetically favourable trans-III conformation. The average Zn—N bond lengths in both macrocyclic units do not differ significantly [2.112 (12) Å for the anion and 2.101 (3) Å for the cation] and are shorter than the average axial Zn—O bond lengths [2.189 (4) Å for phosphonate and 2.295 (4) Å for aqua ligands]. In the crystal, the complex cations and anions are connected via hydrogen-bonding interactions between the N—H groups of the macrocycles, the O—H groups of coordinated water molecules and the P—O—H groups of the acids as proton donors, and the O atoms of the phosphonate and carboxylate groups as acceptors, resulting in the formation of layers lying parallel to the (110) plane.