Towards a Paradigm Shift in the Principles and Practice of Polar Organometallic Chemistry

Polar organometallic chemistry provides an essential toolkit for transforming inert bonds into reactive bonds to make new compounds and materials. Very few aromatic molecules (e.g., pharmaceuticals, agrochemicals, perfumes) are made without polar organometallic chemistry being practiced at some stage in their manufacture. Though this chemistry has a long and successful history, it is currently at an exciting crossroads in its development with seemingly impossible challenges within it now on the verge of becoming possible. This project is designed towards fundamentally reforming the practice of polar organometallic chemistry making it more air and moisture compatible, greener, more atom-economical and sustainable. Research will focus on the synthesis, cultivation and exploitation of new s-block metal multicomponent reagents made by co-complexation protocols. Preliminary work has shown that mixing different components within the same environment (for example, two distinct metal complexes; or one metal but with an assortment of ligands) can lead to useful synergistic effects not possible with unmixed systems. The scope of the chemistry and the ability to construct new compounds and new materials to meet societal needs are thus greatly broadened.

Based on earth-abundant metals, these co-complex reagents will be screened in key organic transformations, focusing on deprotonative metallation and metal-halogen exchange reactions as well as in tandem C-C bond forming methods (as an alternative to more expensive and less environmentally benign transition-metal-mediated approaches) targeting synthetically relevant organic substrates. Stoichiometric reactions will be upgraded to catalytic regimes to establish the ground rules for s-block synergistic catalysis focusing on intramolecular hydroamination reactions of a range of unsaturated molecules.

A key objective of the project is to pioneer and extend the use of multicomponent polar organometallic reagents in Deep Eutectic Solvents (DESs). These DESs will provide more cost-effective, greener and biorenewable reaction media to those volatile organic solvents (VOC's) in which most polar organometallic chemistry is carried out today. Progress in this aim will go a long way to eventually realising the "impossible" challenge in polar organometallic chemistry of synthesising and utilising chemoselective organometallic reagents under air and/or in aqueous media. Dispensing with the need for a dry inert atmosphere would have genuine worldwide implications for the practice of polar organometallic chemistry both in academia and industry.

By designing systems that maximise co-complexation and synergistic effects, we aim to establish transformational approaches based on air/moisture compatible and more sustainable s-block-metal mediated synthesis and to develop the fundamental science underpinning s-block metal cooperative catalysis. While these are ambitious, highly challenging objectives, their level of risk is mitigated by our promising preliminary results. This project aims to deliver unprecedented innovation that will impact every academic and industrial laboratory that practices polar organometallic chemistry with benefits flowing to the general public who use fine, speciality and consumer chemicals on a daily basis made using polar organometallics.

The impact of the work will extend to catalysis and challenging catalysis at that as the metals involved will come from the main group of the Periodic Table. Though often still regarded as esoteric, these earth-abundant metals offer significant advantages over transition metals in terms of abundance, cost, sustainability and greenness. Switching to s-block and early p-block co-complexes as catalysts can have a global impact, leading to potentially novel methodologies that will reduce energy consumption and waste.

The development of innovative strategies using cheap biodegradable solvents as superior alternatives to volatile organic solvents will go a long way to meeting the ultimate challenge of polar organometallic chemistry, that is, to perform it under air or even in aqueous media. Scientifically this will be a seminal breakthrough leading to high impact publications and publicity in academic and popular science forums, with implications for practical applications across many areas of science, from chemistry to biochemistry to materials. The impact of new technologies, mainly based on protic environmentally-friendly solvents like DESs, would be of substantial long term benefit to large multinational industries (e.g. pharmaceutical, agrochemical, and organic materials). Many advantages would be realised including greater sustainability, safer working practices, and large cost savings as well as minimising the use or generation of toxic chemicals. The impact of these new techniques would of course benefit society in general as numerous commodity chemicals (pharmaceuticals, cosmetics, dyes, polymers, etc.) require polar organometallic methodologies in their preparation.

Due largely to the rise of their pharmaceutical markets because of their increased wealth, the BRIC countries are using more and more organolithium reagents (for example, butyllithium plants have recently opened in Gujarat, India and Zhangjiagang, China). What we propose in this project extends far beyond this conventional polar organometallic chemistry so in the longer term these countries could also become important end users of these new technologies.