Octahedral chromium(III) complexes in dipolar aprotic solvents. I. The isomerization of cis- and trans-Dichlorobisethylenediamine-chromium (III) ions in anhydrous NN-dimethylformamide

Abstract

The kinetics and mechanism of the isomerization of cis- and trans- dichloro- bisethylenediaminechromium(III) ions, cis- and trans-[CrCl₂ en₂]⁺, have been investigated in anhydrous NN-dimethylformamide (DNF). The complex cis- chlorodimethylformamidebisethylenediaminechromium- (III), cis-[CrCl(DMF) en₂]²⁺, is found to be a necessary intermediate and to remain a significant part of the system at equilibrium. The equilibria are found to depend on the concentration of free chloride ion as has been found in the comparable cobalt system.    Activation parameters have been determined for isomerization reactions using both the cis- and trans-(CrCl₂ en₂)⁺ ions as starting materials and for the chloride entry reaction into the cis-[CrCl(DMF) en₂]²⁺ ion which has been isolated as cis-[CrCl(DMF) en₂](ClO₄)₂,R₂O.