Inhaltszusammenfassung

Density functional theory (DFT) computations at the B3LYP/Lanl2DZ level were used to elucidate the oxygen atom transfer (OAT) and coupled electron proton transfer (CEPT) reaction steps involved in the biomimetic catalytic cycle performed by polymer-supported (MoO2)-O-VI(NN')(2) complexes [NN' = phenyl-(pyrrolato-2-ylmethylene)-amine] with water as oxygen source, trimethyl-phosphane as oxygen acceptor and one-electron oxidising agents. The DFT method employed has been validated against ...Density functional theory (DFT) computations at the B3LYP/Lanl2DZ level were used to elucidate the oxygen atom transfer (OAT) and coupled electron proton transfer (CEPT) reaction steps involved in the biomimetic catalytic cycle performed by polymer-supported (MoO2)-O-VI(NN')(2) complexes [NN' = phenyl-(pyrrolato-2-ylmethylene)-amine] with water as oxygen source, trimethyl-phosphane as oxygen acceptor and one-electron oxidising agents. The DFT method employed has been validated against experimental data [X-ray crystal structures of a NN' ligand and a (MoO2)-O-VI(NN')(2) Complex as well as kinetic data]. The rate-limiting step in the forward-OAT from [(MoO2)-O-VI] to PMe3 is the attack of PMe3 at an oxo ligand with Delta G(not equal) (298 K) = 64.6 kJ mol(-1). Dissociation of the product OPMe3 is facile with Delta G(not equal) (298 K) = 26.3 kJ mol(-1) giving a mono-oxo [(MoO)-O-IV] complex which fills its coordination sphere with a further PMe3 substrate with Delta G(not equal) (298 K) = 39.2 kJ mol(-1). One-electron oxidation to a Mo(V) phosphane complex precedes the coordination of water/hydroxide. Additionally, the comproportionation of [(MoO2)-O-VI] and [(MoO)-O-IV] to dinuclear oxo-bridged [O=Mo-V-O-Mo-V=O] species has been calculated as the thermodynamic sink in this system and the back-OAT from dmso to mono-oxo [(MoO)-O-IV] to give [(MOO2)-O-VI] has been shown to involve an equilibrium between stereoisomeric [(MOO2)-O-VI] complexes with an activation barrier of Delta G(not equal) (298 K) = 113.1 kJ mol(-1). (C) 2008 Elsevier Inc. All rights reserved. » weiterlesen» einklappen

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DDC Sachgruppe:
Chemie