The crystal structure of potassium (ethylenediamine)bis(oxalato)chromate(III)-potassium iodide–water (1/1/2), K[Cr{C2H4(NH2)2}(C2O4)2]·KI·2H2O

Abstract

The title compound is triclinic, P, a= 9.80(2), b= 10.61(2), c= 7.89(2)Å, α= 90.0(1), β= 108.0(1), γ= 92.5(1)°, Z= 2. Both (+)- and (–)-forms of the optically active complex anion occur in the unit cell. The anions have almost exact two fold axes parallel to b, and these pseudo-two fold axes are common to the structure as a whole. There is also a pseudo-n-glide plane, and the whole arrangement is very nearly P2/n. The values of α and γ reflect this pseudo-symmetry. The conformation of the ethylenediamine ligands is such that their carbon–carbon bonds are nearly perpendicular to the pseudo-threefold axes of the complex anions (Λλ and Δδ) no evidence was found for partial adoption of the other possible conformation. The conformation appears to be determined by electrostatic interaction between the hydrogen atoms and the adjacent iodide ions.