JCJC SIMI 7 - JCJC - SIMI 7 - Chimie moléculaire, organique, de coordination, catalyse et chimie biologique

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

Iron, Copper and non-innocent ligands: a sustainable catalytic alternative to noble metals

In a context of increasingly compelling environmental and sustainability issues, this project is seeking to develop cost-effective alternatives to the use of noble metals in catalytic processes.

Towards a sustainable and eco-compatible catalysis

Ongoing concerns in chemistry gravitate towards the reduction of waste presenting toxicity for the environment, and synthetic chemistry is often seen has the black sheep in this respect. Catalytic processes –which rely on the use of minute amounts of a molecule (catalyst) able to increase efficiency and which by nature, generate less waste- can and should provide innovative solutions to address today and tomorrow’s synthetic challenges. Catalysts containing noble metals such as Palladium, Rhodium, Iridium and Platinum are the most widely used in the industry. However, growing concerns regarding their cost, limited resources and sometimes toxicity have triggered a trend to reinvestigate the use of both cheaper and more environmentally benign metals, among which Copper and Iron are the most popular. Despite a well-developed chemistry and ubiquitous presence in Nature’s own catalysts: metalloproteins, these metals are inherently limited in terms of electronic nature. However, this atavism could be circumvented by the use of redox or non-innocent ligands (NILs), capable of performing electronic storage and supply, thus allowing these metals to perform reactions once forbidden. The goal of this project is to develop the use of non-innocent ligands in catalytic processes and to position Iron and Copper as efficient alternatives to noble metals hegemony.

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.

Project coordinator

Madame Marine Desage-El Murr (UNIVERSITE PARIS VI [PIERRE ET MARIE CURIE]) – marine.desage-el_murr@upmc.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IPCM - UPMC UNIVERSITE PARIS VI [PIERRE ET MARIE CURIE]

Help of the ANR 168,877 euros
Beginning and duration of the scientific project: September 2011 - 36 Months

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