Preparation and Isomerization of Isomers of the l- or d-Aspartato(l-histidinato)cobalt(III) Complex

Abstract
The six isomers of the [Co(l- or d-asp)(l-his)] complex (asp=aspartate ion and his=histidinate ion) have been prepared and the isomerization studied in the absence of any catalyst. The equilibrium mole fractions of these isomers in water has been found for l-transO5cisN5, l-cisO5transN5, l-fac, to be 0.53, 0.06, and 0.41, respectively, those for d-cisObcisN5, d-transO5transN5, and d-fac to be 0.48, 0.01, and 0.51 respectively. The indication is that the relative positions of the six coordinated atoms around a cobalt atom cause these unequal isomer concentration ratios. The isomerisms are dealt with by means of a network of first order reversible reactions and the absolute values of the rate constants at 80 °C have been determined.