Structural studies in metal–purpurate complexes. Part 6. Crystal structures of bis(purpurato)-copper(II) and -zinc(II) hydrates

Abstract

The crystal structures of the title compounds, [CuL₂]·5H₂O (1) and [ZnL₂]·4H₂O (2)(L = purpurate), have been determined at 295 K by X-ray diffraction and refined by least squares to R 0.083 (702 ‘observed’ reflections) and 0.10 (522 ‘observed’ reflections) respectively. Crystals of (1) are orthorhombic, space group Fddd, a= 24.610(8), b= 24.859(9), c= 8.011(3)Å, Z= 8. Crystals of (2) are monoclinic, space group C2/c, a= 10.404(3), b= 25.355(7), c= 9.695(3)Å, β= 114.89(2)°, Z= 4. Both complexes contain ML₂ molecular species together with lattice water molecules. The symmetry of the zinc derivative is close to D_2d, while that of the copper is reduced to D₂. In each of the tridentate ligands, the central nitrogen co-ordination distance to the metal is equal to, or less than, that of the oxygens [Cu–N 1.931(9); Zn–N 2.07(3), 2.14(3); Cu–O 2.421 (6); Zn–O 2.19(2), 2.10(2)Å] whereas in all derivatives previously studied the metal–nitrogen bond is long. In the copper derivative, a better model is obtained if the metal atom is disordered in z over two sites 0.61(1)Å apart; Cu(disordered)–N is 1.954(8), and Cu–O 2.246(8), 2.621(10)Å.