Complexes of meso- and (±)-butane-2,3-diamine with manganese-, cobalt-, nickel-, copper-, zinc-, and lead-(II): a potentiometric, calorimetric, and spectroscopic study
Abstract
The formation constants of complexes of meso- and (±)-butane-2,3-diamine with Mn2+, Co2+, Ni2+, Cu2+, Zn2+, and Pb2+ have been measured potentiometrically at 25 °C and I= 0.10 mol dm–3(K[NO3]), and the enthalpy changes on complex formation with Ni2+, Cu2+, and Zn2+ have been measured calorimetrically. The results are interpreted in terms of the possible conformational differences in the chelate rings and the formation of square-planar bis complexes with Ni2+(particularly with the meso isomer of the ligand) and of tetrahedral bis complexes with Zn2+. The existence of square-planar bis complexes of Ni2+ has been confirmed spectroscopically, and the square-planar–octahedral equilibrium constants have been estimated.