KINETICS OF REACTION OF SOME MONOACIDOPENTAAQUONICKEL(2) COMPLEXES WITH 4-(2-PYRIDYLAZO)RESORCINOL

Kinetics and mechanism of the reaction of monoacetato-, monoazido-, monofluoro-, and monohydroxonickel(II) complexes with 4-(2-pyridylazo)resorcinol have been studied spectrophotometrically at μ = 0.10 and at 25.0°. The reaction scheme can be described as [formula omitted] where A- is a monodentate ligand such as hydroxide, azide, acetate, and fluoride and HR- refers to monoionic species of 4-(2-pyridylazo (resorcinol. The stability constants, KNiA, of the monoacidonickel(II) complexes and rate constants, kH and kA, are kinetically determined: KNiOH = 104.3±0.1, KNiN = 100.66±0.10 KNiO = 100.74±0.15, KNiF = 101.1±0.1, kH = (1.7 ± 0.1) × 103 M-1 sec-1, kOH = (1.0 ± 0.15) × 104 M-1 sec-1, kN = (1.1 ± 0.15) × 104 M-1 sec-1, kCH = (4.5 ± 0.4) × 103 M-1 sec-1, kF = (1.1 ± 0.2) × 103 M-1 sec-1. The difference of reactivity of these nickel(II) complexes is discussed in terms of electron donation of coordinated ligands on the basis of a model in which loss of the first water molecule coordinated to nickel(II) is the rate-determining step. The effect of electron donation of ligands on the rate of loss of water molecule is thus quantitatively accounted for. © 1969, American Chemical Society. All rights reserved.