Kinetics and mechanism of the stoichiometric oxygenation of [CuII(fla)(idpa)]ClO4 [fla=flavonolate, idpa=3,3′-imino-bis(N,N-dimethylpropylamine)] and the [CuII(fla)(idpa)]ClO4-catalysed oxygenation of flavonol

Oxygenation of [CuII(fla)(idpa)]ClO4 (fla=flavonolate; idpa=3,3′-iminobis(N,N-dimethylpropylamine)) in dimethylformamide gives [CuII(idpa)(O-bs)]ClO4 (O-bs=O-benzoylsalicylate) and CO. The oxygenolysis of [CuII(fla)(idpa)]ClO4 in DMF was followed by electronic spectroscopy and the rate law −d[{CuII(fla)(idpa)}ClO4]/dt=kobs[{CuII(fla)(idpa)}ClO4][O2] was obtained. The rate constant, activation enthalpy and entropy at 373 K are kobs=6.13±0.16×10−3 M−1 s−1, ΔH‡=64±5 kJ mol−1, ΔS‡=−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 [CuII(fla)(idpa)]ClO4 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]/dt=kobs[{CuII(fla)(idpa)}ClO4][O2]. The rate constant, activation enthalpy and entropy at 403 K are kobs=4.22±0.15×10−2 M−1 s−1, ΔH‡=71±6 kJ mol−1, ΔS‡=−97±15 J mol−1 K−1, respectively.