Project Description

The aim of NoNoMeCat is to train researchers in the emerging field of Non-Noble Metal homogeneous Catalysis. NoNoMeCat seeks to replace conventional catalysts that are often based on precious metals by catalysts based on the more abundant first row metals.
Transition metal containing compounds are known to catalyse a wide variety of chemical transformations that find use both in research laboratories and in the chemical industry. A large fraction of catalytic processes make use of late second- and third-row transition metals (Ru, Os, Rh, Ir, Pd, Pt). While still largely unequalled in terms of catalytic performance, these metals suffer from a number of drawbacks impacting both industrial actors and society as a whole. First, their scarcity makes their market prices both high and volatile. Second, precious metals are generally toxic both for humans and for the environment. As a consequence, trace amounts need to be thoroughly removed from final products – especially for pharmaceuticals, food additives, cosmetics – and the resulting purifications steps consume energy and produce waste, impacting the monetary and environmental cost of industrial processes.
The last decade has witnessed a widespread effort from the scientific community to develop protocols that circumvent the use of precious metals. Approaches that use no-metal are showing promise in certain fields: frustrated Lewis pairs in hydrogenations, H-bond based organocatalysis in polar organic reactions (aldol condensation, Michael addition, etc.), and photo-redox catalysis for controlled radical reactions. However, as suggested by the fact that more than 50% of enzymes are metalloenzymes, solutions to a broader range of catalytic problems can be expected from systems relying on mid-to-late first-row metals (base metals like: Mn, Fe, Co, Ni, Cu) that are typically cheaper, less toxic, and more benign than their heavier counterparts. Substitution of critical or scarce materials is a priority for Europe: it is for example an important topic in the European Innovation Partnership on raw materials and in the KIC on raw materials as proposed in the strategic research agenda of the European Institute of Innovation and Technology. This is a rapidly expanding new frontier in the field that is of importance for practical reasons (cost and availability, environmental impact, toxicity) but also offers opportunities for the discovery of fundamentally new reactivity. However, progress is challenged by the particular properties of base metals such as their propensity to adopt high-spin states and to undergo one-electron transformations. In addition, base metals tend to form paramagnetic molecules, whose characterization requires specific training. Harvesting the full potential of base metals in homogeneous catalysis requires several challenges to be overcome:

1. The stability of base-metal catalysts is often much lower than of their noble-metal counterparts – as demonstrated by lower turnover numbers (TON) – but it is of prime importance for successful industrial implementation. Thus, understanding the decomposition pathways of catalysts will favour the development of new, robust ligand systems adapted to first-row metals.
2. Poor selectivity often arises from the frequent occurrence of radical pathways in base-metal catalysis. Strategies must be developed in order to a) tame the reactivity of radicals so that the course of a reaction can be directed towards a single, desired product, or b) design ligand systems that avoid radical pathways either by imposing a strong ligand field or by metal-ligand cooperation.
3. Addressing the abovementioned issues will require a detailed mechanistic understanding of the existing reactions. The development of homogeneous catalysis as it is today has tremendously benefited from fundamental studies on the involved organometallic species and reactive intermediates. To guide and inspire the new generation of molecular chemists, we need a clear understanding of the intimate mechanism of key reactions catalysed by base-metals so that the reactions can be rationally improved through ligand design, condition optimization, additives, etc.
4. The scalability of reactions to be developed needs to be taken into account from early stages on. Thus, attention must be paid to the broad availability of all components of catalytic systems (metal, ligand(s), solvent). Besides assuring scalability by sufficient cost and waste efficiency, safety should also be addressed when aiming at scalable new systems.

Main objectives of the NoNoMeCat network