How do organometallic chemists aim to shape the future against the background of new feedstocks, new targets, the developing capabilities of outside fields, and the forces of sustainability that are so essential today?
The topic “Future Faces of Organometallic Chemistry and Homogeneous Catalysis” was selected for the round table discussion sponsored by the European Journal of Inorganic Chemistry (EurJIC) and European Journal of Organic Chemistry (EurJOC) as part of their 20th anniversary activities at the European Conference on Organometallic Chemistry (EuCOMC) in Amsterdam in July. Professor Bas de Bruin, University of Amsterdam (UvA), The Netherlands, and Vice-Chairman of the organizing committee of the conference, selected the panel (see Fig. 1) from invited speakers and chaired the discussion with Professor John Hartwig, University of California, Berkeley, USA, as moderator. John kicked off the discussion with a short presentation as an appetizer of issues for possible consideration. Each panel member added a statement to start the lively discussion.
Figure 1. (from left to right) Hansjörg Grützmacher, Per-Ola Norrby, Bas de Bruin (Chairman), Charlotte Williams, John Hartwig (Moderator), Pedro Pérez.
Impact of Organometallic Catalysis
In the beginning, John made it clear that organometallic catalysis has a large impact on how everything is made. Our world is inconceivable without organometallics. However, other aspects appear to limit their future, which he summarized under the headings Feedstocks, Sustainability, Innovation, Energy, and New Methods.
Present and former petroleum feedstocks or heavy metal containing reagents are limited by availability and toxicity. Different organometallic catalysts might promote the use of new and innovative feedstocks. Professor Per-Ola Norrby, AstraZeneca Gothenburg, Mölndal, Sweden, raised the point that CO2 is the thermodynamic end of all carbon-containing compounds. Therefore, solutions are needed for a CO2-neutral production of fine chemicals. This is the whole point of studying biomass conversions. Perhaps organometallic chemistry can also find ways to make direct use of CO2 from the relatively low sources in the atmosphere or the sea.
Sustainability does not only mean that feedstocks are renewable. In a world plagued by millions who are hungry, renewable feedstocks should not compete with food production. Arguably more significant for sustainability is catalysis that cuts out synthesis steps, because it reduces waste and resources.
A catalytic cycle is not optimal if it is stopped by deactivation. A future challenge is the invention of repair mechanisms for catalysts that are poisoned. Understanding excited states is another challenge. We need to make better use of energy that is locked within molecules with organometallic chemistry.
From the audience the issue of the origin and long-term availability of noble metals was raised. The response of the panel showed that prioritizing these important topics is difficult: Which is the most pressing challenge: replacement of platinum and rhodium catalysts by cheaper metals recovery of noble metals?
Over half of platinum and rhodium catalysts are used in car catalysts and are recoverable. Furthermore, the need for such catalytic converters will drop significantly with the shift to electric cars.
The concerns of Professor Hansjörg Grützmacher, ETH Zurich, Switzerland, introduced a different direction. Modern science must respond to the needs of a modern society. One important task in organometallic chemistry is, for example, addressing the pollution of oceans as a result of the huge use of polymers like polyethylene and polypropylene, which are indestructible by natural means in the short term. We need to make the processes of degrading and recycling polymers more efficient or develop polymers that break down faster in nature. Polymers provide a strong future for organometallic chemistry with respect to design and realizing that design. We need to think in the broadest of terms and not be constricted by the past.
Using organometallic methods, chemists can emulate and vary nature to make complex molecules or, for example, to optimize drugs based on complex natural products and to increase their availability. Organometallic chemistry has changed. It should continue to provide chemists with the tools to change what they make and how they make it. Such a strategy is valid for all molecules pertinent to today’s world. In polymer technology, for instance, adiponitrile is synthesized by hydrocyanation of butadiene. Can this monomer or its co-monomer be made from glucose?
Professor Pedro J. Pérez, Universidad de Huelva, Spain, emphasized that in a fast-moving discipline like the young field of organometallic chemistry, the cutting-edge research will be forward-looking. The next generation must focus on new reactions rather than on innumerable variations of established reactions. This struck a chord with John who added the example of the fundamentally different reactions of hydrogenation of imines and nitriles, which both formally involve a hydride reduction. We need new synthetic tools to perform the same reaction in several ways.
Alternative and sustainable energy solutions need to be found with the help of organometallic chemistry. Professor Charlotte Williams, Oxford University, UK, was inspired by the posters at the conference that showed important problems still to be solved, such as energy generation and storage not forgetting the distribution and transport of energy.
5. New Methods
Flow chemistry or developments outside organometallic chemistry such as the turnkey methods of molecular biology (ready for immediate use) can be friends, not foes. According to Bas, one addition to the organometallic toolbox could be electrochemistry for one-electron oxidation/oxidation-addition processes. We also need to utilize solar energy to make organometallic chemistry more sustainable.
New Directions in Organometallic Research
The audience suggested new directions for organometallic chemistry. Chemical vapor deposition (CVD) and nanochemistry should also be part of an organometallic chemistry conference.
The direction of organometallic chemistry research itself was questioned. At present every lab is doing its own small research projects. The idea that governments should set the priorities with a “Manhattan project” approach prompted an immediate reaction. The answer from the panel was a categorical “no”. The government’s main goal should be to educate young people. The more a government intervenes in research the more time is diverted from research to administration. Chemists must organize themselves and concentrate on exchange of information. They have shown that they can do this: Scientists invented the internet – not to create Facebook but to exchange information.
Nevertheless, to develop this new face of organometallic chemistry, fundamental research needs funding. The microchip that is essential for everyday laptops and smartphones descends from the moon landing technology. Imagine polymerization today without the fundamental studies of Zr metallocene catalysts. Neither was intended for its use in today’s world. How could anybody have guessed where such seemingly esoteric research would lead?
There is still a place for research without the intention of doing something practical, but organometallic chemists must take a good idea and transform it into applications. Similarly, kinetic studies are important to solve problems. An investigation into the mechanism of C–H functionalization led to a catalyst that was employed about a decade after its discovery. How can one discover new mechanisms on purpose? Combining new organometallic chemistry with informatics to discover transformations could be a way forward.
Figure 2. John Hartwig welcomes the participants to the round table discussion sponsored by EurJIC and EurJOC as part of their 20th anniversary activities.
Figure 3. Hansjörg Grützmacher and Per-Ola Norrby during the discission.
The round table discussion was very well received and prompted many discussions over lunch. It succeeded not only in its aim to encourage innovation in the field but in a wider sense the ideas will serve as a reference when writing grant applications.
- Event: European Conference on Organometallic Chemistry (EuCOMC) in Amsterdam in July 2017