Periodic Reporting for period 1 - SINGAMBI (The Single-Centre Ambiphile ligand Concept: Cooperative Systems for Waste-free Catalysis)
Periodo di rendicontazione: 2023-04-01 al 2025-09-30
The addition of ammonia to alkenes, which could produce amines in a 100% atom efficient process, has never been achieved by a molecular catalytic system and stands as a modern Holy Grail for the synthetic chemist. Alkyl amines, a major chemical commodity, are typically accessed through stoichiometric methods, even employing toxic N1 feedstocks such as hydrogen cyanide. The fundamental barrier to utilizing ammonia as an N1 feedstock lies in its activation, with a high N-H bond energy and a preference for acting as a neutral donor ligand in organometallic systems. In order to employ ammonia in catalytic transformations, new bond-activation concepts which address these fundamental pitfalls are essential.
The SINGAMBI project overcomes these challenges through the Single-Centre Ambiphile (SCA) ligand concept. Drawing inspiration from cooperative activation protocols at play in enzymes and bimetallic complexes, this concept defines non-innocent ligand systems which utilise highly reactive ambiphilic species from the forefront of low-valent main group chemistry. In combination with reactive transition metal (TM) centres, SCA ligands provide a platform for cooperative bond scission via yet unexplored mechanistic pathways. This can drive facile ammonia activation, directing N-H bond cleavage towards the formation of TM hydride complexes, key in overcoming previous shortfalls in the hydroamination of alkenes with this abundant small molecule. Ultimately, we will expand this concept towards universal systems for waste-free alkene functionalisation catalysis, through forming a deep understanding of the unique mechanistic pathways accessible through the SCA ligand concept. In designing, developing and understanding numerous SCA-TM systems, the SINGAMBI project will develop a breadth of unique chemical tools for the promotion of cooperative bond activation and sustainable catalysis, framed by the activation and utilisation of ammonia for waste-free access to commodity amines.
The SINGAMBI project overcomes these challenges through the Single-Centre Ambiphile (SCA) ligand concept. Drawing inspiration from cooperative activation protocols at play in enzymes and bimetallic complexes, this concept defines non-innocent ligand systems which utilise highly reactive ambiphilic species from the forefront of low-valent main group chemistry. In combination with reactive transition metal (TM) centres, SCA ligands provide a platform for cooperative bond scission via yet unexplored mechanistic pathways. This can drive facile ammonia activation, directing N-H bond cleavage towards the formation of TM hydride complexes, key in overcoming previous shortfalls in the hydroamination of alkenes with this abundant small molecule. Ultimately, we will expand this concept towards universal systems for waste-free alkene functionalisation catalysis, through forming a deep understanding of the unique mechanistic pathways accessible through the SCA ligand concept. In designing, developing and understanding numerous SCA-TM systems, the SINGAMBI project will develop a breadth of unique chemical tools for the promotion of cooperative bond activation and sustainable catalysis, framed by the activation and utilisation of ammonia for waste-free access to commodity amines.
The project so far has focused on established a broad number of catalyst systems, involving ligand development, exploration of novel transition metal fragments, and screening of their proficiency in waste-free catalytic protocols.
This has led to a number of high-tier publications, two of which are described here. In the first, we were able to develop a new family of ligands based on germanium(II) binding centres. Using simple ligand design concepts, we were able to modulate the bonding nature of these systems. Then, in cooperation with a low-valent nickel centre, we could show that this allows for modulating the energy of reversible dihydrogen activation. This is a key finding for the project, directly demonstrating that the concept laid out in our original proposal are indeed feasible. The energies of this process were quantified by in-depth kinetic methods, and corroborated by computational modelling. Finally, this 'tuneability' was coupled to a catalytic process: we found the all systems can achieve the dehydrocoupling of silanes, with reaction rates depending on the nature of the ligand system.
In the second publication, we demonstrated a facile method for accessing bimetallic Ga-Ni systems, which feature our develop chelating ligands. This is key in stabilising these systems, and driving their chemistry. Here, we found that systems reversibly and cooperatively activate dihydrogen, and can achieve the catalytic selective semi-hydrogenation of alkynes to alkenes. In-depth kinetic and computation studies shed light on the unique cooperative mechanism at play in this system, confirming our hypotheses at the project outset.
This has led to a number of high-tier publications, two of which are described here. In the first, we were able to develop a new family of ligands based on germanium(II) binding centres. Using simple ligand design concepts, we were able to modulate the bonding nature of these systems. Then, in cooperation with a low-valent nickel centre, we could show that this allows for modulating the energy of reversible dihydrogen activation. This is a key finding for the project, directly demonstrating that the concept laid out in our original proposal are indeed feasible. The energies of this process were quantified by in-depth kinetic methods, and corroborated by computational modelling. Finally, this 'tuneability' was coupled to a catalytic process: we found the all systems can achieve the dehydrocoupling of silanes, with reaction rates depending on the nature of the ligand system.
In the second publication, we demonstrated a facile method for accessing bimetallic Ga-Ni systems, which feature our develop chelating ligands. This is key in stabilising these systems, and driving their chemistry. Here, we found that systems reversibly and cooperatively activate dihydrogen, and can achieve the catalytic selective semi-hydrogenation of alkynes to alkenes. In-depth kinetic and computation studies shed light on the unique cooperative mechanism at play in this system, confirming our hypotheses at the project outset.
The above described results are absolutely beyond the state of the art. We have related sub-projects within the ERC StG which also fall firmly into this category - further research is required here to bring those results to fruition, peer-reviewed outputs.
Additionally, we have state of the art findings which may have commercial value. In this regards, we aim to apply for an ERC PoC grant to bring those results to the fore, and better explore their economic viability.
Additionally, we have state of the art findings which may have commercial value. In this regards, we aim to apply for an ERC PoC grant to bring those results to the fore, and better explore their economic viability.