A Novel Chromium(III) Hybrid Salt, Triethylammonium <i>Trans</i>-Diaquabis(Oxalato-<i>κ</i><sup>2</sup>O<sup>1</sup>,O<sup>2</sup>) Chromate(III), (C<SUB>6</SUB>H<SUB>16</SUB>N)[Cr(C<SUB>2</SUB>O<SUB>4</SUB>)<SUB>2</SUB>(H<SUB>2</SUB>O) <SUB>2</SUB>]: Synthesis, Spectroscopic Studies, Thermal Behavior and Crystal Structure

A novel organic-inorganic chromium(III) hybrid salt, triethylammonium trans-diaquabis(oxalato-κ2O1,O2)chromate(III), (C6H16N)[Cr(C2O4)2(H2O)2] (1), has been synthesized in aqueous solution and characterized by elemental and thermal analyses, FTIR and UV-Vis spectroscopies, and by single crystal X-ray structure determination. Compound 1 crystallizes in the orthorhombic system, Pbcn space group with the unit cell parameters a = 11.1776(10), b = 7.6105(10), c = 17.5654(2) Å, α = β = γ = 90°, V = 1494.24(3) Å3, Z = 4 and Z’ = 1/2. The structure of 1 consists of [Cr(C2O4)2(H2O)2]− mononuclear anions and triethylammonium [(C2H5)3NH]+ cations. In the anionic unit, the CrIII ion is six coordinated, in a distorted octahedral geometry, by four equatorial O atoms of two oxalate anions acting as chelating ligands and two O atoms from trans-coordinated water molecules occupying the apical positions with longer metal-oxygen distances. In the solid, O-H … O and N-H … O intra and inter molecular hydrogen bonding interactions connect the components into a 3D network. The triethylammonium cations are disordered among two possible orientations with occupancies rates around 50% for C4, N1, C1a, C1b, C4ii, N1ii, C1aii, C1bii (ii = −x + 1, y, − z + 1/2). The IR spectrum of 1 is consistent with the presence of the various molecular building constituents. 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 studies carried out in air between 25°C and 700°C confirm the anhydrous character of 1 and show that it is stable up to 210°C.