Study of hydrolysis of cis-tetrachlorodi-m-carboxylates of dirhenium (III) was carried out due to the electronic adsorption and IR spectroscopy and pHmeter. As a result, itwas shown that the hydrolysis is a multistage process which can be attributed to the reactions of the pseudo-first order. It is also shown that the electronic absorption spectroscopy (EAS) is a reliable method of investigation to study the hydrolysis of rhenium (III) complex compounds. This conclusion is based on the fact that in the systems with halide and carboxylic ligands, each of the five structural types can be clearly identified by the EAS in the region of both d–d* electron transition and charge transfer transition of L*Hal ®Re type. It is shown that with the increase in the length of the alkyl group and in its branching, the hydrolysis rate decreases, as a result of a change in the positive inductive effect of these groups and, consequently, an increase in the strengthening of quadruple Re–Re bond. In addition, with the help of the EAS, a transition of the chloride ligands to OHgroups can be observed. As a result of the study, a hydrolysis route, which initially leds to the gradual replacement of the chloride ligands of a complex compound with OH groups, and subsequently to the conversion of Re(III) compounds into the derivative of Re(IV) was proposed. The dependence of resistance to hydrolysis on the structure of the complex compound, the temperature and pH was determined. It allowed to predict the stability of the investigated compounds while their usage as biologically active substances and reagents in the synthesis of new compounds. The obtained results allow us to presence of anticancer, cytostabilizing and other biological activities is the coordination of Re(III) complex compounds with the components of biomolecules (proteins, DNA).
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