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)

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Abstract

The complex [Cu(fla)2] has been prepared by treating copper(n) 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 coordination geometry of the copper(n) 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-3s-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.

Original languageEnglish
Pages (from-to)3847-3854
Number of pages8
JournalJournal of the Chemical Society - Dalton Transactions
Issue number21
DOIs
Publication statusPublished - Nov 7 1999

ASJC Scopus subject areas

  • Chemistry(all)

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