Issue 21, 1999

Kinetic studies on the copper(II)-mediated oxygenolysis of the flavonolate ligand. Crystal structures of [Cu(fla)2] (fla = flavonolate) and [Cu(O-bs)2(py)3] (O-bs = O-benzoylsalicylate)

Abstract

The complex [Cu(fla)2] has been prepared by treating copper(II) chloride with sodium flavonolate in tetrahydrofuran solution. Crystallographic characterisation of the complex [Cu(fla)2]·2CHCl3 has shown that the co-ordination geometry around the copper(II) ion is square planar. Oxygenation of [Cu(fla)2] in dimethylformamide solution at ambient conditions gives [Cu(O-bs)2] (O-bs = O-benzoylsalicylate) and carbon monoxide. Crystallographic characterisation of [Cu(O-bs)2] on crystals obtained from pyridine as [Cu(O-bs)2(py)3]·0.91py revealed that the co-ordination geometry of the copper(II) ion is square pyramidal with trans O atoms of O-bs and N atoms of py ligands in basal and an N atom of py in apical position. The oxygenolysis of [Cu(fla)2] in DMF was followed by electron spectroscopy and the rate constants were determined according to the rate law –d[Cu(fla)2]/dt = k[Cu(fla)2][O2]. The rate constant, activation enthalpy, entropy and free energy at 373 K are as follows: k/mol dm–3 s–1 = (1.57 ± 0.08) × 10–2, ΔH /kJ mol–1 = 53 ± 6, ΔS /J K–1 mol–1 = –138 ± 11, ΔG /kJ mol–1 = 105 ± 2. The reaction fits a Hammett linear free energy relationship and a higher electron density on copper results in a faster oxygenation reaction.

Supplementary files

Article information

Article type
Paper

J. Chem. Soc., Dalton Trans., 1999, 3847-3854

Kinetic studies on the copper(II)-mediated oxygenolysis of the flavonolate ligand. Crystal structures of [Cu(fla)2] (fla = flavonolate) and [Cu(O-bs)2(py)3] (O-bs = O-benzoylsalicylate)

É. Balogh-Hergovich, J. Kaizer, G. Speier, G. Argay and L. Párkányi, J. Chem. Soc., Dalton Trans., 1999, 3847 DOI: 10.1039/A905684J

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