Dual Unsaturated Transition Metal-Main Group (TM-M') Heterobimetallic Complexes for Cooperative Reactivity and Catalysis

The transformation of organic molecules is central to the production of the commodities, materials and fine chemicals (such as pharmaceuticals) that underpin modern society. Much research in academic and industrial chemistry is focused on improving the processes by which these products are formed, as well as on designing new transformations to access new products. Efficiencies can be achieved by lowering energy requirements, reducing the number of steps involved, improving process selectivities, or simplifying product separation and purification. These features all serve to reduce the economic
costs and environmental impact of production. Improved or new catalytic processes have a very significant impact when implemented by the UK chemicals sector, a major contributor to the UK economy that has an annual turnover of £60 billion, sustains 500,000 jobs and an annual trade surplus of £5 billion.

>90% of chemicals and pharmaceuticals involve the use of a catalyst in their manufacture. Catalysts work by bringing molecules together and enabling their transformation with reduced energy costs and often improved selectivity. Moreover, the catalyst is unchanged in this process and so can be recycled many times. Catalysis is therefore central to the design of more sustainable processes that will have reduced environmental impact, as greater efficiency results from the ability to start from alternative, more readily available feedstocks, leads to lower energy usage and reductions in waste.

This project explores the design of new complexes with potential in homogeneous catalysis. Homogeneous catalysts generally involve a single central transition metal which acts as the site of reaction and which is surrounded by a number of ligands that control the efficiency and selectivity of the process. More recently cooperative catalysts have been designed where both the metal and a ligand participate directly in the reaction. Another class of cooperative catalyst features two metal centres working in tandem to provide new reactivity and catalysis. These new classes of catalyst have all emerged from curiosity-driven, fundamental research and have served to broaden the pool of catalysts available for applications in synthesis. These have then been taken on by more applied research in academia and industry to exploit in the design of more efficient and new catalytic processes at scale.

In this project we will study a new generation of complexes in which a transition metal (TM = Ru, Rh, Pt...) is directly bound to a main group metal (M' = Zn, Mg, Al...). The properties of these two types of metal centres are very different and in isolation they promote very different reactivity and catalysis. We hypothesize that in combination these new 'heterobimetallic' complexes will promote new reactivity that cannot otherwise be accessed.

Preliminary results have shown that we have a very simple and extremely general strategy to the synthesis of these new TM-M' complexes using a suite of building blocks that are readily, and often commercially, available. There is therefore the potential to make a very large number of new TM-M' complexes. In order to guide our work, we will combine an experimental chemistry approach with computational modelling to provide an understanding how these heterobimetallic complexes promote reactivity. Modelling will then be used to predict stability and reactivity, allowing us to focus our experimental work on those combinations with the most attractive features (high reactivity, high selectivity etc.). We will then assess the ability of these new complexes to promote catalytic reactions and in doing so will add to the pool of catalysts that are available for possible exploitation by applied research in academia and industry.

1. Who will benefit from this research?

The research will have four major sets of beneficiaries: (i) researchers in academia and industry; (ii) PDRAs working on the project; (iii) undergraduate summer students; (iv) the wider public.

2. How will they benefit from this research?

(i) Researchers in academia and industry will benefit from the range of new complexes produced in this project, and in particular those that show potential as catalysts for unusual reactions. Coupling the discovery of new catalysts with the understanding of how these systems work could underpin the design of new catalytic processes for atom economic transformations. In the longer term if such transformations scale, then the chemical industry would benefit from better routes to current products or access to new products. Industry would also benefit from enhanced environmental sustainability through reduced waste and energy usage, aligning industry with government policies on clean growth.

(ii) The PDRAs will benefit from a first-class training in either modern experimental or computational chemistry, as well as from the development of communication, presentation and organisational skills, planning and team working. These will be enhanced through the collaborative nature of this project, as well as by taking responsibility for undergraduate summer projects and the organisation of a research symposium. Outreach activities will also challenge the PDRAs to articulate the excitement and importance of fundamental research to members of the public. The PDRAs will also benefit from enhanced publication records, building on the strong track record of the PIs in disseminating their work in very high impact journals. This, along with the rounded technical and inter-professional skills, will enhance their employability and enable them to contribute strongly to the UK economy in their later careers.

(iii) Undergraduate summer students will benefit from the enhanced experience of research in either experimental or computational chemistry. They will also be supported in improving their communication, presentation and organisational skills, as well as team working between the Heriot-Watt and Bath sites. They will also benefit from an enhanced
engagement with their subject and this, along with their enhanced employability skills, will inform and facilitate their future career choices and prospects.

(iv) The Wider Public. Outreach activities will benefit the public by highlighting how scientific research aligns with topical government policies focused on clean and sustainable growth. School students will gain from knowledge of the opportunities provided by studying STEM subjects and pursuing these into further education and their future careers. More efficient means of chemical production will also benefit the wider public through a long-term enhancement of quality of life associated with new commodities and reduced environmental impact.