Yttrium ethyl-enediammonium squarate tetra-hydrate.

The title compound, {(C(2)H(10)N(2))(1.5)[Y(C(4)O(4))(3)(H(2)O)(4)]}(n) {system-atic name: catena-poly[sesqui(ethyl-enediammonium) [[tetra-aquabis-(squarato-κO)yttrium(III)]-µ-squarato-κ(2)O:O']]}, was synthesized by slow evaporation of an acid solution. The asymetric unit contains one yttrium cation in an anti-prismatic environnement, three squarate groups, one and a half protonated ethyl-enediamine mol-ecules and four water mol-ecules. YO(8) polyhedra are connected through bis-(mono-dentate) squarates, leading to infinite zigzag chains, in between which are located ammonium groups. A framework of hydrogen bonds between protonated amine N atoms, water mol-ecules and squarate anions ensures the cohesion of the structure.

A second monoclinic polymorph of ethyl-enediammonium bis-(hydrogen squarate) monohydrate.

The title compound, C(2)H(10)N(2) (2+)·2HC(4)O(4) (-)·H(2)O, a new polymorph of ethyl-enediammonium bis-(hydrogen squarate) monohydrate, was synthesized by slow evaporation of an acid solution. The asymetric unit contains two hydrogen squarate anions, two half-mol-ecules of protonated ethyl-enediamine arranged around a twofold axis and one water mol-ecule. In the crystal, N-H⋯O and O-H⋯O hydrogen bonds between the hydrogen squarate anions, protonated N atoms from the amine group and water mol-ecules lead to a three-dimensional framework. In particular, the cohesion between the squarate groups is ensured by very short intermolecular hydrogen bonds bonds. The title compound crystallized together with the previously reported polymorph [Mathew et al. (2002 ▶). J. Mol. Struct.641, 263-279].