COPPER(II), NICKEL(II) AND PALLADIUM(II) COMPLEXES OF THE DIAMIDE LIGAND N,N'-BIS(2-CARBAMOYLETHYL) ETHYLENEDIAMINE (H2L) AND THE CRYSTAL-STRUCTURE OF THE CARBONYL-OXYGEN-BONDED COPPER(II) COMPLEX [CU(H2L)](CLO4)(2)

The preparation of the diamide ligand N,N'-bis(2-carbamoylethyl)ethyle nediamine (H2L) by Michael addition of ethylenediamine to acrylamide i s described. The copper(II) complex [Cu(H2L)](ClO4)(2) and the deproto nated complex [CuL]. H2O have been prepared and characterized as has t he blue octahedral nickel(II) complex [Ni(H2L)](ClO4)(2). The crystal structure of the carbonyl-oxygen-bonded copper(II) complex [Cu(H2L)] ( ClO4)(2) has been determined (R = 5.5%). The stepwise protonation equi libria of the ligand have been studied by potentiometric titration, gi ving values of log K-1 = 8.71 and log K-2 = 5.74 at 25 degrees C and I = 0.1 mol dm(-3) (NaClO4). The interaction of copper(II) with the lig and (H2L/Cu(II) = 1:1) can be fitted to the set of equilibria: Cu2+ H2L reversible arrow [Cu(H2L)](2+); log beta(110) = 11.73(3) Cu2+ + H2 L reversible arrow [Cu(HL)](+) + H+; log beta(11-1) = 3.80(4) Cu2+ + H 2L reversible arrow [CuL] + 2H(+); log beta(11-2) = -5.30 With nickel( II), only two complexes, [Ni(H2L)](2+) and [NiL], occur and they have formation constants of log beta(110) = 7.39 and log beta(11-2) = -11.4 9. With palladium(II) the system is similar to that with copper(II) wi th three complex species, 110, 11-1 and 11-2, with log beta(110) = 15. 48, log beta(11-1) = 11.88 and log beta(11-2) = 7.32.