Synthesis, Characterization and Thermal Analysis of an Organic-Inorganic Hybrid Salt Involving Trans-Diaquabis(oxalato-κ2O1,O2)chromate(III) Complex Anion with Piperidinium as Counter Cation

A new organic-inorganic hybrid salt piperidinium trans-diaquabis(oxalato)- chromate(III) tetrahydrate, (C5H10NH2)[Cr(C2O4)2(H2O)2]·4H2O (1), has been synthesized in water and characterized by FTIR and UV-Vis spectroscopies, elemental and thermal analyses and by single-crystal X-ray diffraction. 1 crystallizes in the orthorhombic non-centrosymmetric space group Cmc21 with the unit cell parameters a = 7.4329(3), b = 9.9356(5), c = 23.6756(11) A, α = β = γ = 90°, V = 1748.45(14) A3 and Z = 4. The structure of 1 consists of [Cr(C2O4)2(H2O)2]- mononuclear anions, piperidinium cations and uncoordinated water molecules. The CrIII ion in the complex [Cr(C2O4)2(H2O)2]- is coordinated in a slightly distorted octahedral environment by four O atoms from two chelating oxalate dianions in the equatorial plane, and two O atoms from trans-coordinated water molecules occupying the apical positions. In the crystal, N-H···O and O-H···O hydrogen bond interactions connect the components into a 3-D framework. The IR spectrum of 1 is consistent with the presence of the various molecular building constituents, namely oxalato and aqua ligands, piperidinium cations and solvent water molecules. The UV-Vis spectrum shows two absorption bands around 564 and 416 nm which are compatible with an anionic chromium(III) complex in an octahedral environment. Thermal analysis shows a three-step decomposition of 1, leading to formation of a metal oxide residue.