Cobalt(II), nickel(II) and zinc(II) complexes of 3,3'-[Ethane-1,2-diylbis(imino)]-bis(propanamide) in solution

Abstract

The interactions of 3,3'-[ethane-1,2-diylbis(imino)]bis(propanamide) (H2eip) with cobalt(II), nickel(II) and zinc(II) ions in 0.1 mol 1-1 KNO3 at 25�C have been studied by means of potentiometry. In addition, the nickel system has also been studied by means of spectrophotometry, infrared and 13C n.m.r. spectroscopy. Equilibria (1) and (2) were found to hold: Ni2++H2eip↔Ni(H2eip)2+ (1) Ni2++H2eip↔Ni(H2eip)2H+ For the other metal ions only equilibrium (1) was observed experimentally. The values of the equilibrium constants for cobalt, nickel and zinc are log K1 5.39, 7.59 and 5.05 respectively, and pK1'' 19.24 for nickel. For Ni(H2eip)2+, three absorption maxima were found at γmax 746, 595 and 367 nm with εmax values 6.5, 6.9 and 11.5 cm-1 mol-1l. respectively; for Ni(eip), only one absorption maximum at γmax 446 nm with εmax 91.9 cm-1 mol-1 l. was observed.