Demasking reactions of potassium hydroxotrifluoroborate with lanthanum(III) complexes of polyaminopolycarboxylic acids: Part 1. Equilibrium constants for the reactions with EDTA and NTA complexes

Equilibrium constants for the demasking reactions of potassium hydroxotrifluoroborate. (KBF₃OH) toward La(III) complexes of EDTA and NTA have been estimated by means of ¹H-n.m.r- measurement at 35°C. For the constants defined as K^BF_LaLm = [L]^m[La(BF₃OH)_n]/[LaL_m][BF₃OH]_n, the results were: for EDTA (m = 1,n = $\text{1}\text{3}$) K^BF_LaL = 10^2.7, and for NTA (m = 2, n = $\text{1}\text{3}$) K^BF_LaL2 = 1026. These values are much larger than the equilibrium constants for the well known demasking reaction of fluoride ion toward La(III) complexes of EDTA and NTA, which are —12.43 and —14.92, respectively.