Impact 2-amino-3-metiebutanovoy acid and education a polynuclear complexonates cobalt(II) in aqueous solutions

By absorption spectrophotometry and pH-metry and studied the formation of complexes containing cobalt ions (II), as well as ethylenediaminetetraacetic (EDTA, H$_4$Edta) and 2-amino-3-methylbutanoic acid. The method of mathematical modeling established that to describe the experimental curves absorbance of acidity and concentration of the reactants most likely mathematical models include as parameters hydrolysis constants of Co(II) (K$_{i,r}$), ligand dissociation constants (K$_i$) and stability constants ($\beta$) gomoligandnyh and polynuclear complexes. The constants of equilibrium reactions and the stability constants of the complexes formed. The limits of pH values found of the existence of complexes, as well as their prospective structures and models. In aqueous solution, it was found the presence of the binary and ternary complexes of general structure 1:1 and 1:2 and 1:1:1, 2:2:1, 2:4:1, 3:6:1 and 4:8:1; [CoEdta]$^{2-}$ ($\lg \beta = 16,31 \pm 0,06$), [CoHEdta]$^-$ ($\lg \beta =18,96 \pm 0,02$), [CoVal]$^+$ ($\lg \beta = 4,44 \pm 0,19$), [CoVal2] ($\lg \beta =8,25 \pm 0,09$), [CoValEdta]$^{3-}$ ($\lg \beta = 20,76 \pm 0,05$), [(CoVal)$_2$Edta]$^{2-}$ ($\lg \beta = 31,07 \pm 0,07$), [(CoVal$_2$)$_2$Edta]$^{4-}$ ($\lg \beta = 40,00 \pm 0,17$), [(CoVal$_2$)$_3$Edta]$^{4-}$ ($\lg \beta = 53,76 \pm 0,40$), [(CoVal$_2$)$_4$Edta]$^{4-}$ ($\lg \beta = 68,78 \pm 0,33$). All received constants are valid for the ionic strength I $\approx$ 0.2 (NaClO$_4$) and a temperature of ($20 \pm 2$) $^{\circ}$C.
It demonstrated that octahedral metal ions sphere of polynuclear complexes molecule linked EDTA, which forms a bridge between two diaminoetanovy cobalt atoms in the binuclear complex. The tricyclic complex cobalt atom is attached by two covalent bonds EDTA carboxyl groups. The tetranuclear complex third and fourth cobalt atoms are attached to the bridge structure links the two. One of them — the usual covalent by carboxyl groups OH$^-$, the other — a donor-acceptor due to the carbonyl. The coordination sphere of cobalt atoms contain two valine molecule.