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 [Cu-II(fla)(idpa)]ClO4 (fla = flavonolate; idpa = 3,3'-iminobis(N,N-dimethylpropylamine)) in dimethylformamide gives [Cu-II(idpa)(O-bs)]ClO4 (O-bs = O-benzoylsalicylate) and CO. The oxygenolysis of [Cu-II(fla)(idpa)]ClO4 in DMF was followed by electronic spectroscopy and the rate law - d[{Cu-II(fla)(idpa)}ClO4]/dt = k(obs)[{Cu-II(fla)(idpa)}ClO4][O-2] was obtained. The rate constant, activation enthalpy and entropy at 373 K are k(obs) = 6.13 +/- 0.16 x 10(-3) M-1 s(-1), DeltaH(double dagger) = 64 +/- 5 kJ mol(-1), DeltaS(double dagger) = -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)]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 = k(obs)[{Cu-II(fla)(idpa)}ClO4][O-2]. The rate constant, activation enthalpy and entropy at 403 K are k(obs) = 4.22 +/- 0.15 x 10(-2) M-1 s(-1), DeltaH(double dagger) = 71 +/- 6 kJ mol(-1), DeltaS double dagger = -97 +/- 15 J mol(-1) K-1, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.