WATER EXCHANGE BETWEEN SOLVENT AND AQUOETHYLENEDIAMINENICKEL(2) COMPLEXES

Water exchange rates with Ni(H2O)62+ (pH 6), Ni(H2O)4(en)2+, and Ni(H2O)2(en)22+ are reported. The k1 (25°, sec−1) values for a particular water molecule are 4.4 (±0.2) X 104, 4.4 (±0.2) X 105, and 5.4 (±0.3) X 106, respectively. The corresponding ΔH* values are 10.3 ± 0.5, 10.0 ± 0.5, and 9.1 ± 0.5 kcal mole−1. Scalar coupling constants (A/h) in the same order are 2.2 (±0.4) X 107, 2.2 (±0.2) X 107, and 2.3 (±0.2) X 107 cps. Tle for Ni(H2O)2(en)22+ is ca. 2.5 X 10−12 sec. Some discussion of the effects of water substitution on lability of the remaining water is given. © 1969, American Chemical Society. All rights reserved.