Equilibrium and kinetic study of pyridine binding to phthalocyaninatoiron(II) in dimethyl sulphoxide
- 1 January 1985
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 6,p. 1107-1111
- https://doi.org/10.1039/dt9850001107
Abstract
The reaction between pyridine (py) and phthalocyaninatoiron(II), [Fe(pc)], in dimethyl sulphoxide (dmso) has been studied from the kinetic and the equilibrium viewpoints at 20 ± 0.5 °C. In the presence of a large excess of pyridine the adduct [Fe(pc)(py)2] is formed via pseudo-first-order kinetics. The observed rate constants have the general form kobs.=k1f[py]+k1r, with k1f′≈ 1.5 × 104 dm3 mol–1 s–1 and k1f″= 35.5 ± 0.7 dm3 mol–1 s–1 and k1r″= 0.15 ± 0.02 s–1, for the binding and dissociation of the first and second py molecules, respectively. From the values of the equilibrium constant [K1′=(3.9 ± 0.1)× 105 dm3 mol–1] and of the second-order rate constant (k1f′) for the binding of the first py molecule, the dissociation rate constant has been estimated to be k1r′≈ 4 × 10–2 s–1. The value of the equilibrium constant for the binding of the second py (K1″= 300 ± 28 dm3 mol–1), determined directly, is in good agreement with the corresponding value (240 ± 40 dm3 mol–1) obtained from the ratio k1f″/k1r″). The data obtained in the present study are discussed in the light of related previous studies.Keywords
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