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Cooperative Catalysis: Using Interdisciplinary Chemical Systems to Develop New Cooperative Catalysts

Periodic Reporting for period 4 - CoopCat (Cooperative Catalysis: Using Interdisciplinary Chemical Systems to Develop New Cooperative Catalysts)

Reporting period: 2022-08-01 to 2024-01-31

The main problem tackled by this project is the limitation of our current industrial chemical processes to face key challenges as chemical sustainability. Industry highly relies on catalytic processes, but from a technical point of view, most of the available ones are not proficient enough regarding several fundamental aspects such as activity, selectivity, substrate scope or cost efficiency.
The importance of catalysis to chemical industry is evinced by the fact that 75% of all chemicals currently require catalysts at some stage in their production, with catalytic processes generating €1,000 Bn in products world-wide. Therefore, the development and fundamental understanding of innovative catalysts will have direct and long-term benefits to the chemical manufacturing sector and to the broader knowledge-based economy.
The overall aim of this ERC project is to develop innovative cooperative catalysts using interdisciplinary chemical systems based on main group elements, transition metals and molecular clusters to achieve better efficiency and improve chemical scope and sustainability of key chemical transformations. To achieve this aim, the main objectives of the project are:
- To explore bond activation and catalysis using Frustrated Lewis Pairs constructed around transition metals (TM-FLPs).
- To synthesize hybrid systems based on low-valent main group elements and transition metals (Hybrid TM/MG) to investigate their catalytic applications through synergistic effects.
- To design and characterize a library of supramolecular Intercluster Compounds (ICCs) to be used as heterogeneized materials for Green Catalysis.
- To build innovative chemical super-architectures capable of performing unprecedented catalytic transformations.
The following paragraphs cover the work carried out within this ERC project from February 2018 to the end of the project (see Figure).
Objective 1: We have investigated many bimetallic FLP combinations and acquired a deep understanding on how they operate. Some of them activate rather strong bonds (Chem. Commun. 2019). In addition, our mechanistic investigations allowed us to provide evidence for the genuine frustrated character of our gold/platinum TMFLPs (CEJ2020), while subtle modifications of the ligands permit rational control of regioselectivity (Organometallics 2020, 2021; Chem. Commun. 2022). Our Lewis acid/base bimetallic combinations have also allowed us to identify the non-innocent character of the very common Cp* ligand (Angew. Chem. 2020; JACS, 2019, Dalton Trans. 2023, Inorg. Chem. 2023). Also, we have started to explore bimetallic FLPs based on Earth abundant metals (Angew. Chem. 2022). Our continuous interest on accessing extremely bulky and electrophilic synthons led us to discover a novel mechanism for C-C bond formation (JACS, 2021) and to disclose a highly constrained cavity-shaped gold system (Chem. Commun. 2021, ACS Catal. 2022, ChemPlusChem 2022, Inorg. Chem. 2022). Additionally, our attempts to access radical FLPs led us to an intriguing open-shell Ir(II) system (Angew. Chem. 2022).
Objective 2: We have examined the coordination chemistry of sterically congested germylene compounds with a variety of transition metals. From there, we have obtained dynamic information from X-ray diffraction studies on metalogermlenium cations (CEJ2020), demonstrated the potential of TM-Ge cooperation during bond activation (CEJ2021) and catalysis (ChemCatChem 2022, Chem. Commun. 2022). We investigated the synthesis and tuning of their clusters (CEJ 2024). The combination of alkali and transition metals was also explored (Chem. Sci. 2022). In addition, we have investigated the reactivity of a gold/platinum FLP towards tetrylene dihalides (combining WP1 and W2; Dalton Trans. 2019). With the same spirit of combining WP1 and WP2 we have explored the bonding in metal-only Lewis pairs formed between a Rh(I) Lewis base and main group Lewis bases (CEJ2020).
Objective 3: We have prepared a number of transition metal clusters. We have combined cationic versions of these clusters with commercial polyoxometalates and obtained a family of heterogeneous intercluster compounds. Despite our success in synthetic aspects, the prepared materials do not show remarkable results in terms of catalysis yet. We continue exploring other related systems, as described in our contingency plans (e.g. Molecules, 2020).
Objective 4: We have not yet found catalytic applications of the cooperative systems targeted in WP4. Some of them have been prepared, but their characterization is rather difficult and still evolved into nanoparticles which, although interesting, were beyond our scope. We have explored an alternative approach based on solid-state organometallic chemistry based on extremely bulky systems that still holds the porosity of a molecular heterogeneous material and that set the grounds for much future work in our group. The first contribution is currently under evaluation.
Objective 1:
- We have gained solid mechanistic support for the first truly frustrated system entirely based on transition metals.
- We have reported the first bimetallic system that efficiently activates both O-H and N-H bonds in water and ammonia, respectively.
- We have demonstrated that subtle modifications of steric parameters in bimetallic frustrated Lewis pairs can have dramatic effects on regioselectivity during bond activation processes.
- We have extended the library of bimetallic frustrated Lewis pairs far beyond their previous development, including earth-abundant metals.
- We have evinced the usefulness of using bimetallic approaches to isolate otherwise fleeting intermediates.
- We have disclosed a rather unusual reactivity for an open-shell Ir(II) system that will serve as a seed to develop the first bimetallic frustrated radical pairs
- We have demonstrated a positive effect of confinement in fundamental gold organometallic chemistry and catalysis.

Objective 2:
- We have isolated the first examples of hybrid transition metal/low-valent heavier main group elements based on NP bifunctional ligands
- We have synthesized a number of transition metal/tertrylene systems with unprecedented structural features and reactivity
- We have made use of structural data from X-ray diffraction studies to gather fundamental information on dynamic processes for arene π-bonding in tetrylenes
- We have demonstrated that hybrid TM-Ge systems can effect positive effects on catalysis, in particular in terms of selectivity during hydrogenation and hydrosilylation reactions
- We have demonstrated that cluster structures based on TM-tetrylene fragments can be finely tuned by exogeneous bases

Objective 3:
- We have demonstrated that the combination of cationic and anionic clusters produce highly insoluble intercluster compounds that show potential for catalytic applications.
- We have provided a robust and versatile method to access trimetallic complexes based on trisphosphinite ligands.
- We demonstrate that our approach to heterogenize molecular clusters led to POM-decorated nanoparticles in most cases

Objetive 4:
- We have demonstrated that the combination of extremely bulky fragments of positive and negative charges provide access to porous molecular materials with potential for bond activation and catalysis
General image of the work done