COMPLEX SPECIES IN AQUEOUS SOLUTION OFMETA-PHENYLENEDIAMINE-N,N,N′,N′-TETRAACETIC ANDPARA-PHENYLENEDIAMINE-N,N,N′,N′-TETRAACETIC ACIDS IN THE PRESENCE OF COPPER(II)

Tetraaqua-μ4-(phenylenediaminetetracetato-O1:O2:O3,O4,N:O5,O6,N1)-dicopper(II) dihydrate

“…These ligands can, therefore, coordinate in two spheres and are potentially tridentate. This is in accordance with our studies in aqueous solution of the coordinating capacity of m-and p-phenylenediamine-N,N,N,N'tetraacetic acid with Cun (Mederos, Felipe, Brito & Bazdikian, 1986) and with the structure of the title compound, described in this work.…”

Dimer species in aqueous solutions of m–phenylenediamine-N,N,N′,N′-tetra-acetic acid (m-H4pdta) with copper(II) and of pyridine-2,6-diamine-N,N,N′,N′-tetra-acetic acid (2,6-H4pydta) with nickel(II). X-Ray crystal structures of Na4[Cu2(m-pdta)2]·18H2O, Na4[Co2(m-pdta)2]·10H2O, and Na4[Ni2(2,6-pydta)2]·8H2O

“…The model that best fits the experimental results corresponds to the complex species in Table 2. From the values obtained for the constants PP4, corresponding to equilibrium (12) the stability constants K could readily be determined. pH+ + qNi2+ + rH3L-e [H,Ni,(H L),](P' 2 q -')+ (12) Although models were tested that included the possible presence of complex species with an excess of metal and with an excess of ligand (1igand:metal ratio 3: 1, cM = 1 x lC3, 2 x lW3, and 3 x lW3 mol dm-3, respectively), the results indicate that they are not present in significant amounts.…”