Properties of some ethylenediamine cobalt complexes coordinated with dicarboxylic acids and related compounds

Abstract

Coordination compounds of the type [coen2AA] were prepared by known methods where AA = cartonate, Y = chloride, bromide, iodide, perchlorate, nitrate, thiocyanate, dithionate and sulphate; AA = oxalate, Y = bromide; AA = malonate, Y = bromide and maionate; AA = succinate, Y = bromide and perchlorate. The infrared spectra of these complexes were measured and also of complexes of the type trans - [Coen2Cl2] AA where AA = oxalate, maionate and succinate. The spectra of the cis-complexes were found to fall into two classes and possible reasons for this are discussed. The visible and ultraviolet spectra of the complexes were measured and also the change in these spectra when alkali and acid were added to solutions of the complexes.The base hydrolysis of the complex [Coen2CO2CH2CO2]Br was studied at hydroxide concentrations of about 0.1M and 1M and at temperatures in the range 38°- 55° and was found to follow second-order kinetics with an activation energy of 29,000 cals mole. The maionato complex was optically resolved giving the dextrorotatory iodide and the optical rotatory dispersion of this optical isomer was measured. This isomer was found to be stable in neutral solution but lost its optical activity in basic solution at the same rate as the base hydrolysis. The mechanism of the base hydrolysis and loss of optical activity is thought to be similar to that of the oxalato complex as suggested by Taube.