Catalysis underpins all of the research within the North group. We both use existing catalysts and develop and study new ones. As green chemists, our focus is on sustainability of the catalyst itself as well as the feedstock it is used to transform. For example, the bimetallic aluminium(salen) catalyst show in the section on carbon dioxide capture and utilisation is derived from aluminium, one of the most abundant metals in the Earth’s crust. In contrast, many current catalysts are based on ‘endangered’ metals such as rhodium, ruthenium and platinum. The periodic table shown above highlights that only six metals can be considered as Earth crust abundant.
The use of catalysts derived from sustainable elements is a long established theme in my research and is an area we continue to expand. Thus, the aluminium complex shown above will also catalyse the addition of other heterocumulenes (carbon disulfide, isocyanates etc) to epoxides, providing a versatile route to a range of five-membered ring heterocycles. Ongoing work is expanding the range of heterocycles that can be made in this way and providing mechanistic information on the reactions. We are also using similar complexes derived from titanium and vanadium as catalysts for asymmetric carbon-carbon bond forming reactions including asymmetric cyanohydrin synthesis and asymmetric Michael additions.
Another catalysis theme within the North group is avoiding the use of metals altogether and focussing on purely organic catalysts. As an example, we have shown in collaboration with the group of Yuri Belokon’ in Moscow that the well-known dye crystal violet will catalyse the synthesis of cyclic carbonates from epoxides and carbon dioxide.