METAL-LIGAND COOPERATIVE CATALYSIS BASED ON ORIGINAL NON-INNOCENT PINCER COMPLEXES – CYCLOOP

Cooperative catalysis, in which both partners work in a concerted manner to favor a transformation, has become a highly valuable synthetic tool. Inspired by biological systems, several types of cooperativity involving transition metals have been designed: bimetallic, metal/organic and metal/ligand. This project aims at the development of new cooperative metal/ligand systems and their application in catalytic processes other than hydrogenation/deshydrogenation. We have chosen to focus on non-innocent pincer complexes. One of the originalities of the present proposal is based on the strong synergy between theoretical and experimental approaches.
Starting from preliminary results using “indenediide/Pd” catalytic system in the cycloisomerization of alkynoic acid, we now seek the optimization of the catalytic performances (selectivity and activity) of pincer complexes so that more challenging substrates can be envisioned. In order to achieve this goal, we will take profit of the high structural modularity of indenediide and methanediide pincer ligands, developed by two of the partners. In a first step, the theoretical tool will be used to explore the possible catalytic mechanisms in order to identify steps/parameters influencing the activity and the selectivity. Experimental mechanistic investigations and stoichiometric reactions will complete the computational studies. This will help to evaluate the impact of the structural modulations on the non-innocent character of the ligands and thereby the catalytic performances. The best candidates will be tested first in the formation of valuable alkylidene lactones via cycloisomerization of alkynoic acids, including internal alkynes or those leading to medium and macrolactones. These systems will be evaluated subsequently in even more challenging cyclization processes such as those involving alkenoic acids, ynamides or alkynols.
These cyclization processes using the designed non-innocent pincer complexes provide an ideal route for the preparation of lactones for the ring opening polymerization (ROP), (in particular 7-membered ring lactones). epsilon-lactones will be prepared from alkynoic or alkenoic acid and their use in ROP will be explored aiming at preparing biodegradable polyesters with tunable properties. Cyclic bloc copolyesters are particularly targeted, and a dual “metal/organic base” catalytic polymerization approach recently described by partner 1 will be used. These cyclic copolymers draw a growing attention due to their different physical properties compared to the linear counterparts. We target in particular cyclic copolymers with non-miscible blocs capable of phase-segregation in nano-structures. Original cyclic block copolymers will be thus prepared and their properties of nanostructuration will be compared with those of the linear ones.