Kinetics and thermodynamics of fast square-planar–octahedral inter-conversion. Part II. Influence of the basicity and steric hindrance of heterocyclic amines in the reaction with [biacetyl bis-α-hydroxybenzyl-idenehydrazone(2–)-N1N1′OO′]nickel(II) in chlorobenzene

Abstract

A comparative thermodynamic and kinetic study has been made of reaction (i)[bbh = biacetyl bis-α-hydroxy- [graphic omitted] (i) benzylidenehydrazone(2–)-N¹N¹′OO′ L = 4-cyano-, 3-chloro-, 2-methyl-, 2,4-dimethyl-, and 3,5-dimethyl-pyridine, morpholine, or piperidine] in chlorobenzene. Apart from a drastic steric-hindrance effect, variations of the structure and basicity of the amine have little effect on the values of the rate constant k₁, which refers to the release of one molecule of amine from the octahedral complexes as in (ii). The values of k₁, are correlated with the [Ni(bbh)L₂] [graphic omitted] [Ni(bbh)L]+ L (ii) equilibrium constants K for reaction (i). Rate and activation parameters associated with reactions (ii) are discussed. Thermodynamic parameters ΔH^⊖, ΔS^⊖, and δG^⊖ obtained for reaction (i) in chlorobenzene are also discussed and compared with the analogous values for reaction in benzene.