DETERMINATION OF EQUILIBRIUM AND KINETIC CONSTANTS IN PENTACYANO-L-FERRATE SYSTEMS BY CHEMOMETRIC ANALYSIS OF SPECTROSCOPIC DATA

The formation stability constant of the [(FeI)-I-I(CN)(5)NH3](3)- ion was determined by measuring complete UV-vis spectra for different equi librated mixtures of [(FeI)-I-I(CN)(5)H2O](3)- and NH3. The difficulti es associated with overlapping of the equilibrium components was treat ed with adequate processing programs, based on chemometric techniques (factor analysis). By similar calculation procedures, the standard red ox potential of the [Fe-III,Fe-II(CN)(5)L](2,3-) complexes (L = NH3, H 2O) were also obtained through spectroelectrochemical measurements. Th e overall information allowed for an estimation of the stability const ant of [Fe-II(CN)(5)NH3](2-) by employing a thermodynamic cycle. Final ly, the method was extended to the treatment of successive, simultaneo us protonation equilibria in the [Fe-II(CN)(9)pz](3-) ion, as well as to an elementary kinetic; application, namely the dissociation of NH3 from the [Fe-II(CN)(5)NH3](3-) ion.