Iron Catalyzed Double Bond Isomerization: Evidence for an FeI /FeIII Catalytic Cycle

Chemistry. 2021 Apr 1;27(19):5972-5977. doi: 10.1002/chem.202004980. Epub 2021 Mar 15.

Abstract

Iron-catalyzed isomerization of alkenes is reported using an iron(II) β-diketiminate pre-catalyst. The reaction proceeds with a catalytic amount of a hydride source, such as pinacol borane (HBpin) or ammonia borane (H3 N⋅BH3 ). Reactivity with both allyl arenes and aliphatic alkenes has been studied. The catalytic mechanism was investigated by a variety of means, including deuteration studies, Density Functional Theory (DFT) and Electron Paramagnetic Resonance (EPR) spectroscopy. The data obtained support a pre-catalyst activation step that gives access to an η2 -coordinated alkene FeI complex, followed by oxidative addition of the alkene to give an FeIII intermediate, which then undergoes reductive elimination to allow release of the isomerization product.

Keywords: homogeneous catalysis; iron; isomerization; reaction mechanisms; redox chemistry.