ON THE DIOXIMINE COMPLEXES OF TRANSITION- METALS - AQUATION KINETICS OF THE HALOGENO COMPLEXES OF THE TYPES OF [CO(EN)2AX]N-( AND [CO(DIOX H)2XZ]N)

The aquation kinetics of no-amino-bis-ethylenediamino-cobalt(III)-comp lexes in acidic and basic media, as well as assisted by heavy metal io ns in compared to the aquation of halogeno-bis-dioximino-cobalt(III)-c omplexes at constant temperature. The aquation rate of the halogeno-bi s-dioximino-complexes diminishes in the order Cl > Br > I. On the cont rary in the case of the ethylenediamino complexes the iodine derivativ e cannot even be prepared and the aquation rate of the bromo derivativ e is much higher than that of the chloro one. With [Co(en)2AX]2+ type complexes the k(Br)/k(Cl) ratio of the rate constants can be correlate d with the basicity constant of the amine A and discussed in terms of electronic effects. The activation parameters (enthalpy and entropy) s how a kinetic compensation effect in the case of all the reaction type s studied. On the basis of the mean values of activation parameters, a s well as of the compensation parameters one may presume the aquation of the ethylenediamine derivatives investigated to occur in acidic med ia according to an S(N)1, in basic media according to an SN2 mechanism . Their aquation assisted by Hg2+ and Tl3+ ions, as well as the aquati on of the dioximino complexes seem to occur according to some intermed iate type associative mechanism, similar to each other.