The Crystal Structure of d-Tris-ethylenediamine-cobalt(III) Bromide Monohydrate, d-[Co en3]Br3·H2O, and the Absolute Configuration of the d-Tris-ethylenediamine-cobalt(III) Ion, d-[Co en3]3+

Abstract

Abstract The absolute crystal structure of d- [Co en3]·Br3·H2O was determined by means of X-rays. The space group is P43212-D48, with four formula units in a cell of the dimensions a=9.95 and c=16.73Å. The complex ion takes the “lei” form designated by Corey and Bailar and is in the same configuration as had been determined previously. The structure can be most easily described as consisting of layers of complex ions, two types of bromine ions and water molecules perpendicular to the c-axis. The water molecules link the positive and negative ions to form a layer. A definition of “absolute structure” and “absolute configuration” was proposed. The absolute structure was determined by means of the X-ray absorption edge technique of Bijvoet. CuKa rays were used to observe visually the effect of the anomalous dispersion between the reflections (hkl) and (hk\barl), and quantitative measurements of the effect were attempted for some reflections. The absolute configuration of the complex ion deduced from the absolute structure of the crystal is in agreement with the one previously determined for the crystals d- and l-2[Co en3]Cl3·NaCl·6H2O.