Use of Non-Innocent Ligands complexes as VERSatile ALternatives to noble metals – UNILVERSAL

The strategy used for this project relies on a multidisciplinary approach including organic synthesis, catalysis, theoretical calculations and thorough spectroscopic characterization of the systems obtained. Design and preparation of families of non-innocent (redox) ligands will first be targeted along with the preparation of the Copper and Iron complexes. Catalysts will then be tested in high potential catalytic endeavours and results will be rationalized through theoretical calculations and extensive spectroscopic studies.

We have developped an unprecedented application of iron complexes bearing bisiminopyridine non-innocent ligands in tandem C–H activation/arylation. The mechanism of this reaction has been studied by spectroscopy and DFT calculations, and has been shown to proceed as a mimic of noble metal catalytic systems. This mechanism is disctinct from the previously reported ones as it relies on ligand-centered instead of substrate-centered radicals, with the non-innocent ligand acting as an electronic reservoir.

We plan to continue targeting synthetic applications, among which C–H activation, by developping catalytic systems involving complexes of new families of non-innocent ligands with iron and copper.

This work has led to the publication of a review in the European Journal of Inorganic Chemistry : Non-Innocent Ligands: New Opportunities in Iron Catalysis (Blanchard, S.; Derat, E.; Desage-El Murr, M.; Fensterbank, L.; Malacria, M.; Mouriès- Mansuy, V. Eur. J. Inorg. Chem. 2012, 376-389).

The tandem C—H activation/arylation results will shortly be submitted for publication.

The tremendous contribution of organometallic catalysis to modern synthetic chemistry over the last decades has allowed to solve long-standing issues associated with efficiency and selectivity in a host of chemical reactions. In this regard, noble metal-based catalysts have so far gained undisputed leadership and now belong to the classic repertoire of synthetic methods. However, increasing concerns regarding cost and sustainability-related issues are now driving chemists to revisit the chemistry of their neglected cousins: late first-row transition metals. The electronic configuration of these metals makes them prone to mono-electronic transfers, which limits their use in true broad-scope synthetic methodologies, but this atavism could be circumvented by the use of redox or non-innocent ligands (NILs). These molecular scaffolds can act as a storage and supply unit of electrons, allowing the metal to perform reactions once forbidden. This projects aims at bringing the chemistry of redox ligands in the field of applied catalysis through an interdisciplinary approach and will focus on the chemistry of copper (Cu) and iron (Fe). In this perspective, we plan to synthesize several families of novel triazole redox ligands with tunable electronic and steric features through a click-chemistry based approach. DFT calculations will help us validate our structures and the reactivity of the resulting complexes will then be assessed in oxidation processes. Spectroscopic studies including EPR, UV-vis, SQUID measurements and IR will give us insights on the mechanism at stake. With a well-established catalytic system, we will then target carbon-carbon and carbon-heteroatom forming reactions through C-H activation pathways and cycloisomerizations.