Síntese, caracterização e estudo cinético da aquação do complexo nitrato de tetra(amin) carbonatocobalto (III) hidratado [Co(CO3)(NH3)4]NO3. H2O

Abstract

The FTIR and XRD techniques were used to characterize the complex carbonatetetraminecobalt (III) nitrate hydrate, which was obtained from the compound cobaltous nitrate hexahydrate (Co(NO3)2.6H2O). The work aimed at the kinetics study of the complex substitution reaction of the carbonate for the water using UV-Vis, which, with their spectra, there was the electronic transitions of the original complex in the 363 nm wavelength, higher-energy transition that occurs from 1A1g → 1T2g, and 524 nm, lower energy transition that occurs from 1A1g → 1T1g. In the spectra of the compound after the substitution reaction of the carbonate for the water it was no longer possible to see the band at 524 nm and the band of 363 nm there was a large increase in absorbance. Thus, the complex formed has only a transition permitted by spin at 363 nm concerning the transition from 1A1g → 1T1g and the metal band of the charge transfer to the binder (MLCT). With the absorbance data, it was determined that the substitution reaction of the carbonate for the water to the carbonatetetraminecobalt (III) nitrate hydrate follows the law of pseudo first order. From this, the reaction rate constants for each study temperature were found and their behavior was expected, the constant k increased with increasing temperature, except for a dubious result, which should be repeated for better reliability. The value for the activation energy was found to be 61.78 kJ.mol-1, indicating a rapid exchange of binder.