Abstract
A series of potentially tetradentate and pentadentate ligands modelled on BPMEN has been prepared and their iron(II) bis(triflate) complexes have been isolated and characterised by spectroscopic and crystallographic techniques (BPMEN = N,N'-bis(pyridylmethyl)ethylenediamine). Changes to the BPMEN ligand have invariably led to complexes with different coordination modes or geometries and with inferior catalytic efficiencies for the oxidation of cyclohexane with H2O2. The reaction of an iron(II) complex containing a pentadentate BPMEN-type ligand with O2 has resulted in ligand degradation via oxidative N-dealkylation and the isolation of a bis(hydroxo)-bridged dinuclear iron(III) complex with a picolinate-type ligand.
Highlights
Catalyst deactivation is a common but often ignored problem in catalyst development, in particular in oxidation catalysis
Oxidative ligand degradation of a homogeneous molecular oxidation catalyst during its lifetime can be a limiting factor for high turnover and the activity of the catalyst is often directly related to its stability under the oxidising reaction conditions
A thorough understanding of the various oxidative ligand degradation processes will be essential for the design and development of more robust oxidation catalysts
Summary
Unraveling the origins of catalyst degradation in non-heme iron-based alkane oxidation†. A series of potentially tetradentate and pentadentate ligands modelled on BPMEN has been prepared and their iron(II) bis(triflate) complexes have been isolated and characterised by spectroscopic and crystallographic techniques (BPMEN = N,N’-bis(pyridylmethyl)ethylenediamine). Changes to the BPMEN ligand have invariably led to complexes with different coordination modes or geometries and with inferior catalytic efficiencies for the oxidation of cyclohexane with H2O2. The reaction of an iron(II) complex containing a pentadentate BPMEN-type ligand with O2 has resulted in ligand degradation via oxidative N-dealkylation and the isolation of a bis(hydroxo)-bridged dinuclear iron(III) complex with a picolinatetype ligand
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