Kinetics and mechanism of the stoichiometric oxygenation of [Cu II(fla)(idpa)]ClO 4 [fla=flavonolate, idpa=3,3′-imino-bis( N, N-dimethylpropylamine)] and the [Cu II(fla)(idpa)]ClO 4-catalysed oxygenation of flavonol

Abstract

Oxygenation of [Cu II(fla)(idpa)]ClO 4 (fla=flavonolate; idpa=3,3′-iminobis( N, N-dimethylpropylamine)) in dimethylformamide gives [Cu II(idpa)( O-bs)]ClO 4 ( O-bs= O-benzoylsalicylate) and CO. The oxygenolysis of [Cu II(fla)(idpa)]ClO 4 in DMF was followed by electronic spectroscopy and the rate law −d[{Cu II(fla)(idpa)}ClO 4]/d t= k obs[{Cu II(fla)(idpa)}ClO 4][O 2] was obtained. The rate constant, activation enthalpy and entropy at 373 K are k obs=6.13±0.16×10 −3 M −1 s −1, Δ H ‡=64±5 kJ mol −1, Δ S ‡=−120±13 J mol −1 K −1, respectively. The reaction fits a Hammett linear free energy relationship and a higher electron density on copper gives faster oxygenation rates. The complex [Cu II(fla)(idpa)]ClO 4 has also been found to be a selective catalyst for the oxygenation of flavonol to the corresponding O-benzoylsalicylic acid and CO. The kinetics of the oxygenolysis in DMF was followed by electronic spectroscopy and the following rate law was obtained: −d[flaH]/d t= k obs[{Cu II(fla)(idpa)}ClO 4][O 2]. The rate constant, activation enthalpy and entropy at 403 K are k obs=4.22±0.15×10 −2 M −1 s −1, Δ H ‡=71±6 kJ mol −1, Δ S ‡=−97±15 J mol −1 K −1, respectively.