Mixed ligand chelates of UO22+ and VO2+ with catechol as primary ligand and succinic, adipic itaconic, phthalic, 3,5-dinitrosalicylic and 5-sulphosalicylic acids as secondary ligands

The stability constants of binary complexes and ternary complexes of uranyl and vanadyl with catechol as a primary ligand and succinic, adipic, itaconic, phthalic, 3,5 dinitrosalicylic and 5-sulphosalicylic acids as secondary ligands have been determined in aqueous medium by potentiometric titration technique at 300 +- 0.10 and μ = 0.1M (NaClO4). Both the ions individually form 1:1 complexes with all the secondary ligands. Vanadyl forms 1:2 complex with catechol and 3,5-dinitrosalicylic acid only. The ternary chelates are formed by simultaneous equilibrium. The values of Δlog K, Ksub(DXY) Ksub(2XY) or Ksub(2YX) for the ternary complexes have been calculated. It is observed that Ksub(2XV) and βsub(XY) depends on the pK values of the secondary ligands and the binary stabilities respectively. The plot of βsub(XY)/UO22+ versus βsub(XY)VO2+ is linear with slope = 0.96, indicating that the factors affecting the ternary chelates of uranyl and vanadyl ions are almost identical. (author)