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Non-Noble Metal Catalysis - NoNoMeCat

Periodic Reporting for period 2 - NoNoMeCat (Non-Noble Metal Catalysis - NoNoMeCat)

Reporting period: 2018-01-01 to 2019-12-31

Catalysis is a key enabling technology for the development of green and sustainable production processes in the chemical industry. Because catalysis allows for chemical reactions to follow routes that require less energy and are more selective, the impact of catalysis on the overall sustainability of the chemical industry is very large. Accordingly, catalysis is a key technology in the overall sustainability targets of the EU.

Transition metal catalysts are important tools towards greener chemistry, allowing for low-waste, energy-efficient, and selective chemical reactions. Currently, the noble metals (e.g. Ru, Rh, Pd) that are most common in homogeneous catalysts suffer from high toxicity and environmental impact, in addition to their scarcity and ensuing high cost. First-row metals (Mn, Fe, Co, Ni, Cu) are emerging as environmentally benign alternatives, but to this day rarely equal the performance of their noble counterparts.

The NoNoMeCat network aimed at providing interdisciplinary training to a generation of young researchers in the field of Non-Noble Metal homogeneous Catalysis, who will push the boundaries of the field in terms of catalyst stability, selectivity, mechanistic understanding, and scalability. These challenges are addressed in three areas of high fundamental and practical significance: i) the oxidation of hydrocarbons (WP1), ii) the formation of new C-X bonds (C-C, C-N) bonds through cross-coupling reactions (WP2), and iii) clean energy production (WP3). NoNoMeCat has enrolled 13 Early Stage Researchers (ESRs) who received structured training in experimental and theoretical aspects of non-noble metal chemistry, as well as in transferable skills such as research integrity, scientific communication and public outreach. Tight integration of non-academic and industrial partners in the network exposed all ESRs to aspects of both fundamental interdisciplinary research and industrial application.

Overall the most important outcomes of the NoNoMeCat encompass: i) the high-level training and education of young researchers in the emerging field of non-noble metal catalysis (all ESRs involved will or have already received a PhD degree in this field), ii) new scientific insights in a number of catalytic reactions of key strategical importance for which non-noble metal catalysts can be used, iii) the creation of a true intersectorial network of academic and industrial researchers with a shared interest and expertise in the field of non-noble metal catalysis, and finally iv) the creation of a communal pedigree for a group of young researchers that provides them with a firm and collegial professional network for the future.
The main objectives for work package 1 WP1 were the development of challenging oxidation reactions beyond the scope of traditional substrates. Largely driven by the structure and function of natural enzymes able to catalyse such reactions, synthetic catalysts based on metals like Fe and Mn were developed and studied. Typical catalytic reactions include direct C–H bond activations to form alcohols, phenols, and heterocycles.
A highlight of the results obtained within this work package is the development by the Costas group (Girona) in collaboration of the Klein Gebbink group (Utrecht) of a set of Mn catalysts that can stereoselectively oxidize unactivated methylene groups to lactones in high enantioselectivities (up to 99%; see Figure 1). The discrimination of diastereotopic C–H bonds can be modulated by design of the Mn-catalyst without erosion of enantiomeric product excess.

WP2 focussed on the catalytic construction of C–C and C–N bonds, which will enable the selective and sustainable construction of e.g. pharmaceuticals. Encompassing the traditional synthetic protocols based on metals like Pd, Ru, and Pt, conceptually new non-noble metal catalysts were developed for these reactions.
A highlight of the work on this topic is the development by the Hu group (EPFL) of a new catalytic protocol for the synthesis of alkyl amines by metal-catalyzed cross-coupling of alkyl electrophiles with nitrogen nucleophiles (see Figure 2). This protocol employs tandem photoredox and copper catalysis to enable the cross-coupling and allows for rapid functionalization of natural products and drugs.

WP3 focused on the development of novel catalysts for reactions that are related to the global energy problem, such as the production of H2 as an energy carrier and universal reducing agent, and the catalytic reduction of CO2. Electrons (electricity) and light were used as reagents for the development of catalytic procedures.
A highlight of this work package is a study of the Junge group (LIKAT) on a unifying approach to apply molecular catalysts for CO2 reduction using both photochemical and electrochemical methods (see Figure 3). In this study, Mn-diimine catalysts are reported that show an interplay between the two methods. In the photochemical method, carbon monoxide (CO) is selectively generated as the reaction product in very high turn-over numbers. An electrode (electricity) in combination with a weak Brønsted acid can also do the job.

Overall the network has resulted in a plethora of scientific results that aid to further develop the field, have led to a number of scientific publications in leading peer-reviewed journals, provided promising starting points for further development and exploitation, and will in the end lead to 14 PhD theses in the field. Next to the scientific publications, numerous efforts have led to the dissemination of these results and of the network as a whole. A highlight is the publication of the book ‘Non-noble Metal Catalysis’ by Wiley publishers (DOI:10.1002/9783527699087 see Figure 4).
Research within the NoNoMeCat network has resulted in a number of achievements that progress beyond the current standing in the field. Highlights include the development of new oxidation catalysts for the oxidation of methylene groups to alcohols, the catalytic formation of amines from redox-active esters and imines, and the catalytic reduction of CO2 to CO.
Progression of the research program throughout the duration of the network has continuously resulted in the development of new and advanced catalysts in each of the work packages. The unique combination of the expertise in catalysis with the expertise in spectroscopy and computational chemistry within the network has been pivotal in this progression. The tight interaction and collaboration with the industrial network partners has clearly pointed out the general interest of the chemical industry in homogeneous catalysts based on non-noble metals and the potential application of such catalysts in industrial processes.
WP2 Highlight
Book: Non-Noble Metal Catalysis
WP1 Highlight
WP3 Highlight