Premium
The EDTA Complex of Oxidoiron(IV) as Realisation of an Optimal Ligand Environment for High Activity of FeO 2+
Author(s) -
Bernasconi Leonardo,
Baerends Evert Jan
Publication year - 2008
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200701135
Subject(s) - chemistry , dissociation (chemistry) , ligand (biochemistry) , reactivity (psychology) , moiety , hydroxylation , aqueous solution , density functional theory , ground state , crystallography , computational chemistry , stereochemistry , medicinal chemistry , organic chemistry , atomic physics , enzyme , medicine , biochemistry , physics , alternative medicine , receptor , pathology
A prerequisite for the high activity of the FeO 2+ moiety as a hydroxylation agent is that its ligand environment stabilizes the 3σ*↑LUMO, which dominates the reactivity of this system. Features in the ligand environment that promote the reactivity of FeO 2+ are: weak equatorial ligand field to obtain a quintet ground state that stabilizes the unoccupied 3σ*↑; weak axial ligand field to stabilize the 3σ*↑; a positive overall charge to lower the 3σ*↑. Generalised gradient‐corrected Density Functional Theory (DFT) calculations for the series of oxidoiron compounds of composition [FeO · EDTAH n ] ( n –2)+ , with n = 0, 1, 2, 3, 4, show that in particular the complex with n = 4 (charge +2) realises such an environment. Hypothetically, these species may appear as intermediates in the degradation of EDTA and related organics in aerated aqueous Fe II /EDTA solutions. A strong dependence of the C–H activation properties in the hydroxylation of methane on the overall charge of yielding the lowest C–H dissociation barriers. In the n = 4 case, C–H dissociation occurs with anactivation energy of ca. 7 kJ mol –1 , which is below the value computed for the corresponding reaction catalysed by [FeO(H 2 O) 5 ] 2+ (23 kJ mol –1 ). This enhanced catalytic activity is explained by EDTAH n (2– n )– satisfying the listed requirements for an effective ligand, in particular by the very weak axial coordination by the EDTA nitrogen atoms due to large Fe–N distances.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)