Diiron(III) oxo-bridged complexes with BPMEN and additional monodentate or bidentate ligands: Synthesis and reactivity in olefin epoxidation with H2O2

The reactivity of a series of diiron(III) complexes (1–5) of the tetradentate ligand bpmen (N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine) has been investigated. Three new diiron(III) complexes (3–5) with fluoride and acetate ligands have been isolated and structurally characterized. Complex Fe2(III)(μ-O)(μ-OH)(bpmen)2 (1), which contains a μ-oxo, μ-hydroxo diiron(III) diamond core, was found to catalyze the epoxidation of cyclooctene with hydrogen peroxide, but its μ-oxo, μ-acetate counterpart Fe2(III)(μ-O)(μ-OAc)(bpmen)2 (2) is unreactive. The effect of additives such as hydrofluoric acid, tetrabutylammonium fluoride, acetic acid and acetate on the reactivity of 1 and 2 is reported. Complexes 3–5 with two monodentate ligands (F− or OAc−) attached to the bpmen-supported μ-oxo bridged diiron(III) core do not activate H2O2 for olefin epoxidation.

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