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 Fe 2 (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 Fe 2 (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 H 2 O 2 for olefin epoxidation.