Development of Biomimetic Iron-Based Catalysts for Group Transfer & Insertion Reactions Involving Fe=O/Fe=NR as key intermediates

Iron is the most abundant transition metal on Earth. It is a key metal of a large variety of enzymes responsible for performing important and highly challenging reactions, with high valent iron oxo (Fe=O) intermediates oftenly involved. Fe=O, along with its electronic analogue iron imido species (Fe=NR), are highly reactive intermediates which are capable of performing a wide range of oxygenation and amination reaction through group transfer or insertion reactions. The synthesis and study of biomimetic Fe=X (X = O, NR) complexes have thus been a research field of intensive efforts.

The reactivity, selectivity and stability of Fe=X species are closely related to their electronic structures, which is further highly dependent on their supporting ligand set. For an Fe=X with ideal properties to be obtained, a number of factors, mainly concerning the ligand(s), must be judicially integrated: coordination geometry of the metal rendered by the ligand; ligand field strenth, charge and sterics of respective equatorial and axial ligand donors, etc.

The present research project aims to develop anionic multidentate ligands with rigid backbones to support a highly oxidizing Fe=NR moiety. Incorporation of redox-active functionalities into the ligand framework is also a key consideration in some of the ligand to be synthesized, which is believed to provide an electron-reservoir for the reaction process hence mitigating negative effects associated with unfavorable oxidation state fluctuation of the metal center. Various spectroscopic techniques in combination with quantum chemistry calculations will be employed to detect key species and understand their electronic structures to aid for further development of ligand sets and metal complexes/catalysts.