Synthesis, Crystal structure and Characterization of a New Oxalate Chromium (III) Complex

Abstract

A new hybrid salt (C5H9N2)[Cr(C2O4)2(H2O)2].3H2O, 3,5-dimethylpyrazole Cis diaquadioxalatochromate(III) trihydrate, has been prepared by slow evaporation at room temperature and characterized by single crystal X-ray diffraction, IR, UV–visible spectroscopies, PXRD and thermogravimetric analyses. Furthermore, the observed crystal morphology was compared to the simulated one using the Bravais-Friedel, Donnay-Harker model. The structure of the title compound consists of [Cr(C2O4)2(H2O)2] − mononuclear anions, 3,5-dimethylpyrazole cations and three uncoordinated water molecules. The Cr 3+ ion is six coordinated in a slightly distorted octahedral environment, by two O atoms from two water molecules and four O atoms of two oxalate anions acting as chelating ligands. The cohesion of the structure is established by intermolecular O–H...O, N–H...O hydrogen bonds which connect ionic entities and water molecules and also by π– π stacking interactions between the rings of 3,5-dimethylpyrazole cations. Hence, both coordinated and uncoordinated water molecules play an important role in the hydrogen-bonding system and stabilize the structure. Fragments of the molecular structure of the complex show clearly the intermolecular N–H...O and O–H...O hydrogen bonds between the cation, the complex anion and the lattice water molecules which contribute to the cohesion of the ionic structure, leading to a three dimensional network.