Bio-inspired Iron and Manganese Complexes with N2Py2 Ligands: Towards Their Practical Use in Catalytic Oxidations

Abstract

C–H and C=C bond oxidations constitute essential transformations in organic synthesis and in many biological and industrial processes. In the past decades numerous non-heme iron enzymes have been discovered and identified, that are able to conduct biological C–H and C=C bond oxidations via O2 activation in a very selective manner. Inspired by these enzymes, many efforts have been spent on modelling catalytic iron sites and active intermediates involved in catalysis, in order to achieve these oxidation reactions by molecular catalysts outside the enzyme environment. Depending on the ligand, the coordination chemistry and reactivity of synthetic non-heme iron complexes may be drastically different; accordingly, the development of ligands is of pivotal importance to the field. So far, iron complexes with tetradentate nitrogen (N4, generally aminopyridine) ligands have shown to be most successful in achieving highly regio- and stereoselective oxidation reactions utilizing H2O2 as the oxidant. Amongst them, iron complexes with a cis-α topology derived from linear bis-alkylamine-bispyridine (N2Py2) ligands have been proven to be most effective so far. This thesis describes several ligand modifications of the N2Py2 ligand platform, with the aim of either improving C–H oxidation selectivities or enhancing the lifetimes of Fe(N2Py2) complexes in oxidation catalysis. Furthermore, the practical use of the Fe(N2Py2) and Mn(N2Py2) complexes in the oxidation of a number of biologically or industrially relevant compounds, like steroidal derivatives, unsaturated fatty acids and their esters, and vegetable oils, is also investigated in this thesis.