Hydrogen bonding in the chain-like coordination polymer ZnC 4O 4·4H 2O: A neutron diffraction study

Abstract

Monoclinic crystals of ZnC 4O 4·4H 2O were grown in an aqueous silica gel: lattice constants a = 901.2(2) pm, b = 1333.6(3) pm, c = 674.6(2) pm, β = 99.33(2)°, Z = 4, space group C2 c . Anisotropic refinement on single-crystal neutron diffraction data led to R w = 0.0294 including anharmonic thermal parameters for hydrogen atoms and oxygen atoms of the water molecules. The coordination polyhedron of Zn 2− is a slightly distorted octahedron formed by four water molecules and two O squarate atoms which are bound in the trans position to the C 4 ring of the dianion (ZnO, 207.6(1)–212.6(1) pm). Infinite chains consisting of Zn 2+ and C 4O 2− 4 are the main feature of the crystal structure. Adjacent chains are connected by asymmetric hydrogen bonds between H 2O and the O squarate atoms. The squarate dianion is ideally planar. The crystallographically independent CO bond lengths are identical (2 × 125.0(1) pm) although the O squarate atoms are differently coordinated by Zn 2+ and H. The CC bond lengths are slightly different (146.4(1) and 146.7(1) pm).