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The Combination of Electrochemistry and Nickel Catalysis: New Bond-Forming Reactions on a Sustainable Platform

Periodic Reporting for period 1 - ElectroNick (The Combination of Electrochemistry and Nickel Catalysis: New Bond-Forming Reactions on a Sustainable Platform)

Reporting period: 2018-05-01 to 2020-04-30

Throughout the design of new molecules for pharmaceutical and agrochemical applications to benefit society, the formation of carbon–carbon bonds represents a key strategy to combine chemical groups together. However, many of these methods use metal atoms, which become waste at the end of the reaction. To overcome this, chemists use catalysts which can produce multiple equivalents of the new carbon–carbon bond for every molecule of metal catalyst, improving the efficiency and sustainability of the reaction. In particular, electrocatalysts have recently become an important tool towards sustainability in organic chemistry reaction design, using a cheap and efficient supply of electricity to drive the reaction and limit waste.

To this end, ElectroNick aims at establishing a suite of new electrocatalytic carbon–carbon bond formation reactions using nickel complexes as efficient catalysts for synthesis. Reactive intermediates can be forged within the reaction mixture, limiting the waste of metals such as zinc and cobalt. Not only will these reactions improve sustainability in organic synthesis, they will provide the possibility of designing the synthesis of new carbon–carbon bonds with high efficiency and selectivity. However, in order to design these new catalytic systems, it is important to build a deep understanding of the multiple steps within each catalytic cycle, and how subtle changes in the metal complex or substrates that form the new carbon–carbon bond affect overall reactivity. ElectroNick has utilized cutting-edge techniques in electroanalysis and ‘big data’ science to understand these intricate effects, laying the groundwork for future synthetic applications.
ElectroNick commenced with a study into using cobalt electrocatalysts to create cobalt–carbon bonds, which could then transfer the organic group onto a nickel catalyst that would be key to forging novel carbon–carbon bonds. However, when we reduced the Co(II) species, adding an electron from the electrical curcuit to generate a Co(I) intermediate, we found these new Co(I) compounds were very unstable to decomposition, which would not be productive in our desired transformation. To understand this decomposition event, we used advanced electronalytical techniques to study the rate of the reaction. Changing the ligand bound to Co(I), we surveyed how small differences affected this decomposition rate, collecting large data sets to correlate with structural features of the ligand. In doing so, we developed a mechanism for the undesired decomposition pathway, and gained insight in how to avoid it.
With that in hand, we used the same toolkit to understand how the Co(I) would react productively with organic molecules, developing understanding on how, of many possibilities, the Co(I) would add into a carbon–bromine bond (oxidative addition). This strategy of combining electroanalytical techniques with statistical modeling to understand these processes represents a significant advance in building methods to interrogate reactivity, and we have expanded its use to investigating reactivity with alternative substrates and nickel complexes. Finally, the statisical modeling techniques were utilized to understand intricate interactions which drive selectivity in a new palladium catalyzed transformation, forging new carbon–nitrogen and carbon–oxygen bonds towards pharmaceutical targets.
Altogther, ElectroNick has thus far afforded five publications in scientific journals, was presented at two interantional conferences, and been disseminated to the wider public through social media and outreach activities.
ElectroNick is offering a new platform for designing reactivity by combining electroanalytical techniques and statistical modeling to build a thorough understanding of the intricate effects which affect reaction mechanisms. Work in this vein continues to build a global model to comprehend how electrocatalysts interact with organic substrates, facilitating future rational deisgn by the synthetic community. Additionally, ElectroNick has used statisical modeling tools to interrogate a new synthetic transformation, with possible applications in pharmaceutical synthesis. The researcher has developed key skills, both scientific/technical (electroanalysis, statistical modeling) and transferable (dissemination, mentorship, outreach), which will be key to the continued success of ElectroNick in the upcoming return phase. The researcher will disseminate these skills to colleagues in Europe, advancing the scientific community. Specifically, he will be able to implement his knowledge of electroanalysis and statistical modeling learnt during time in the laboratory of Prof. Sigman into understanding mechanisms of nickel reactions with the Martin group at ICIQ. Finally, the work conducted throughout ElectroNick has focused on designing new sustainable chemical transformations; this goal of societal sustainability will be the legacy our generation leaves to benefit those of the future.
ElectroNick Results