N-heterocyclic carbene–nickel(II) catalysts supported on materials of SBA-15 type for C-H bond functionalization – SBA-15-NHC-NiCat
Cheap green catalysts for a sustainable chemistry
Development of cheap and robust catalysts anchored on a solid surface (in order to facilitate their recycling) for clean reactions allowing the synthesis of high value-added organic products from commercially available low reactive reagents.
Inexpensive and recyclable catalysts for economically and environmentally viable reactions
Compelling economic and environmental demands are presently driving fundamental changes in the design of chemical processes. In this regard, the quest for reactions that are satisfying from both cost and atom economy has never been as intense as nowadays. In addition, the relative dearth of non-polluting, recyclable and inexpensive catalysts for the syntheses of fine organic chemicals on large scales generates an increasing demand for supported versions (i.e.: anchored on a solid surface, and thus recoverable by simple filtration) of the soluble molecular catalysts usually used in fine organic chemistry. Indeed, catalysts significantly add to the product costs, and therefore their regeneration and/or reuse are highly desirable.<br />In this context, the project’s goal was the immobilization onto solid supports of soluble molecular catalysts for the synthesis of high value-added organic products from basic reagents. Its originality relied: 1) on the nature of the target reaction, which had to be ecologically benign and economically attractive, 2) on the nature of the molecular catalyst, which had to be inexpensive and robust, and 3) on the immobilization method, which had to generate materials that should allow excellent activity and recyclability of the catalyst.
To reach the fixed goals, the project was composed of three parts.
The 1st part had for goal the development of nickel (which is a cheap metal) based soluble molecular catalysts for C–H bond functionalization reactions, which are reactions that are both economically and environmentally interesting for the synthesis of high value-added organic products directly from basic reagents (i.e.: that do not require expensive and polluting synthetic intermediates), but are essentially developed with expensive noble metals.
The 2nd part had for goal the development of hybrid organic-inorganic support materials with controlled distribution and robust anchoring of the nickel fixation units by an original one step route.
Finally, the 3rd part had for goal the metalation of these novel materials with the appropriate nickel source to give the supported analogues of the soluble molecular catalysts that will have been developed during the first part, and the study of their catalytic activity, stability and recyclability in the target reactions.
The results obtained for the 1st part have gone beyond our expectations, as 3 families of nickel-based soluble molecular catalysts give remarkable results in 5 reactions that allow the preparation of high value-added organic products. The 2nd part has also been fully validated with the development of a model procedure for the one-step synthesis of a hybrid organic-inorganic support material with a regular distribution and robust anchoring of the nickel fixation units. The study of the 3rd part has however not started yet. Nevertheless, the global philosophy of the project has already allowed the generation of a new partnership on a related project for which a patent registration has just been filed.
The expected scientific advances are in conjunction with the aforementioned objectives. At term, we should thus be able:
(i) to replace soluble expensive noble metal catalysts by nickel catalysts in some C–H bond functionalization reactions,
(ii) to obtain hybrid organic-inorganic materials with controlled distribution and robust anchoring of the metal fixation units, which may be used with a large variety of metal compounds,
(iii) to obtain supported molecular catalyst that may be viable in industrial processes from both economic and environmental standpoints.
Our scientific production stands to date to 5 publications in high-impact factor peer-reviewed journals with 2 articles in Chemical Communications (IF = 6.378), 1 article in Advanced Synthesis & Catalysis (IF = 6.048), 1 article in Dalton Transactions (IF = 3.806), and 1 article in Catalysis Science & Technology (IF = 3.753). At least 3 other publications are expected in the near future. In addition, the project has given rise to 4 oral and 4 poster communications in national and international congresses.
The overall goal of this project is to develop inexpensive, truly recyclable and reusable catalysts for which use in industrial processes for the syntheses of fine organic chemicals may be feasible on both economical and environmental grounds. To achieve this goal, we propose a project whose originality relies on a three-feet basis: (i) on the nature of the target reaction, which must be satisfying from both the points of views of cost and atom economy, (ii) on the nature of the molecular catalysts, which must be both inexpensive and robust, and (iii) on the immobilization method, which will generate original materials that are expected to allow excellent activity and recyclability of the supported catalysts.
The activation of C–H bonds towards the formation of C–C bonds is currently one of the most active fields of chemical research. This work is motivated by the desire to develop green and sustainable processes. In particular, the direct arylation of arene C–H bonds is now recognized as an economically and environmentally attractive alternative to the traditional cross-coupling reactions with organometallic reagents. However, it is mainly developed with expensive noble metals such as Pd, Rh and Ru. We therefore propose here to develop inexpensive catalysts based on air-stable electron-rich N-heterocyclic carbene–nickel(II) complexes for the (hetero)arylation of heteroarenes through the cleavage of C–H bonds.
In parallel to this work, heterogenization of organosilylated versions of the N-heterocyclic carbene (NHC) ligand precursors onto SBA-15 mesoporous silica will be pursued by directly co-hydrolyzing them with tetraethoxysilane in the presence of various poly(alkylene oxide) tri-block copolymers as structure-directing agents. This outstanding one-pot approach should lead to mesostructured hybrid organic-inorganic materials of SBA-15 type with controlled distribution of the NHCs, which will very likely exhibit peculiar properties. Subsequent metallation of the best-suited hybrid mesoporous materials (as determined by structural analyses) with the appropriate nickel source will then lead to the expected supported NHC-nickel(II) catalysts, whose catalytic activity, stability and recyclability will be studied in the aforementioned C–H bond functionalization reactions. The reaction scope of the best SBA-15-supported NHC-nickel(II) catalysts that will emerge from these results will then be studied in more details. In particular, reactions that have an industrial importance will be targeted.
Monsieur Vincent RITLENG (CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE ALSACE) – email@example.com
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.
CNRS CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE ALSACE
Help of the ANR 177,525 euros
Beginning and duration of the scientific project: - 36 Months