The Crystal Structure of Tripotassium bis(Oxalato)dioxovanadate(V) Trihydrate

Abstract

The potassium salt of bis(oxalato)dioxovanadate(V), K3[V(O)2(C2O4)2]•3H2O crystallizes in a triclinic lattice with space group [Formula: see text] Two formula units make up the asymmetric unit which has dimensions a = 7.851(2), b = 11.603(2), c = 7.778(2) Å, α = 94.26(1), β = 110.07(1), γ = 91.25(1)°. Three-dimensional single-crystal X-ray diffraction counter data was refined by full-matrix least-squares techniques to R = 0.039. Hydrogen atomic parameters were included in the 213 variables used. A total of 3869 reflections was measured of which 85.4% were classed observed by the criterion I ≥ 2.3σ. The 563 unobserved reflections were included in the final cycle of structure-factor calculations but were not used in the refinement.The anion has irregular octahedral geometry with the two double-bonded oxygen atoms (V=O, 1.628(2) and 1.639(2) Å) cis to each other. The V—O (oxalate) bonds are of two significantly different types: (i) those that are trans to each other (2.009(2), 1.995(2) Å) and (ii) those that are trans to oxo ligands (2.158(2), 2.230(2) Å). The non-coplanar oxalate ligands are twisted about the C—C single bonds (1.550(3) and 1.551(4) Å), while the terminal C—O bonds average to 1.226(9) Å, and the inner ones to 1.274(16) Å. The anions exhibit an approximate non-crystallographic two-fold axis, though distortions from regularity are found. These distortions may best be attributed to hydrogen bonding with the three water molecules and, to a much lesser extent, by contact with the potassium ions.