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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - CoopCat (Cooperative Catalysis: Using Interdisciplinary Chemical Systems to Develop New Cooperative Catalysts)

Teaser

Summary

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 â‚¬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.

Work performed

The following paragraphs cover the work carried out within this ERC project from February 2018 to August 2019 (see Figure).

Objective 1: Transition metal frustrated Lewis pairs. We have extended our preliminary results on the FLP-like activation of small molecules by Gold/Platinum couples to other combinations of transition metals that include the use of Pd, Ni, Rh and Ir as metallic bases and Ag, Cu and Zn as the corresponding acids (J. Am. Chem. Soc. 2019, 141, 2205 and others to be published soon). We have demonstrated that some of these pairs are capable of activating not only the H-H or acidic C-H bonds but also other polar bonds less amenable to cleavage by transition metals such as O-H and N-H bonds in water and ammonia, respectively (Chem. Commun., 2019, 55, 8812). In addition, our mechanistic investigations allowed us to provide evidence for the genuine frustrated character of our gold/platinum TMFLPs (to be submitted shortly), while subtle modifications of the ligands permit rational control of regioselectivity. We have also analyzed the ambiphilic behavior of other homobimetallic species and their capacity to activate small molecules (Chem. Commun., 2018, 54, 9186).

Objective 2: Hybrid main group/transition metal elements. We have synthesized a family of transition metal/germylene species stabilized by a series of phosphinoamide bifunctional ligands. We have found, however, that all prepared complexes are inactive towards small molecule activation and thus catalysis. In parallel, we have examined the coordination chemistry of sterically congested germylene compounds with a variety of transition metals. Although this approach was started recently, we believe that fruitful outcomes will come in the next future, since the preliminary reactivity of these hybrid pairs show great potential. In addition, we have explored the reactivity of a gold/platinum frustrated Lewis pair towards tetrylene dihalides (combining Objectives 1 and 2), revealing an interesting Sn-mediated phosphine exchange reaction and formation of hybrid clusters (Dalton Trans. 2019, 48, 9127).

Objective 3: Supramolecular intercluster compounds. We have prepared a number of transition metal clusters of Ir and Ru, as well as others based on Rh and Au. 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 will continue exploring other related systems, as described in our contingency plans, in the following months.

Final results

The following paragraphs cover progress beyond the state of the art within this ERC project from February 2018 to August 2019. It has been divided in three sections as per Objectives 1-3 described above, providing a bullet list of achievements that go beyond the state of the art.

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 extend the library of bimetallic frustrated Lewis pairs far beyond their previous development

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

Objective 3:
- We have demonstrated that the combination of cationic and anionic clusters produce highly insoluble intercluster compounds that show potential for catalytic applications.

Overall, expected results for the next future in the three aforementioned objectives will involve the implementation of already investigated bond activation processes into catalytic applications.