Sir John Meurig Thomas

First published: 31 May 2013

https://doi.org/10.1002/anie.201303486

Citations: 2

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“My greatest achievement has been to combine being a teacher, a researcher, and a popularizer of science for over 50 years. My worst nightmare is to find myself dumbstruck when I am about to give a lecture …︁” This and more about Sir John Meurig Thomas can be found on page 10938.

References

1“Design, Synthesis, and In Situ Characterization of New Solid Catalysts”: J. M. Thomas, Angew. Chem. 1999, 111, 3800–3843;
10.1002/(SICI)1521-3757(19991216)111:24<3800::AID-ANGE3800>3.0.CO;2-1
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Angew. Chem. Int. Ed. 1999, 38, 3588–3628. This article, a summary of my lecture at the Karl Ziegler Centenary Celebrations at Mülheim (1998) and my Linus Pauling Lecture at Caltech (1999), describes how, by taking open-structure, microporous and mesoporous solids, one may controllably assemble single-site heterogeneous catalysts (SSHCs) that may be readily explored, in situ, with synchrotron radiation and other techniques (notably FTIR) so as to reveal the local atomic environment of the active center and, at the same time, explore the long-range order of the matrix to which it is attached. SSHCs offer a strategy for the precise design of new catalysts. The SSHCs I describe in the paper encompass the reactions: aerobic oxyfunctionalization of terminal groups in linear alkanes; low-temperature selective aerobic oxidation of cyclohexane; radical-free epoxidation of alkenes; Bayer–Villiger oxidations of ketones; preferential dehydration of methanol to yield ethane and propene; and enantioselective allylic aminations. This article explains the key role that solid-state chemistry has to play in heterogeneous catalysis.
10.1002/(SICI)1521-3773(19991216)38:24<3588::AID-ANIE3588>3.0.CO;2-4
CAS PubMed Web of Science® Google Scholar
2“Heterogeneous catalysts obtained by grafting metallocene complexes onto porous silica”: T. Maschmeyer, F. Rey, G. Sankar, J. M. Thomas, Nature 1995, 378, 159–162. Herein we took advantage of the newly available large-diameter family of mesoporous silica, and the SiOH groups on their inner surface, to prepare SSHCs, where titanol groups were shown (by in situ X-ray absorption and FTIR spectroscopy) to be tripodally grafted onto the silica. Using the technique of combining X-ray absorption and X-ray diffraction developed earlier with Neville Greaves, we could follow each single step of the formation of the HOTi(SiO)₃ active center and its subsequent behavior during epoxidation of cyclohexene with an alkylhydroperoxide. The oxidation state of titanium (Ti^IV) could be directly determined, as well as bond lengths and the expansion of the initial four-coordinated active center to a six-coordinated one during the steady-state epoxidation. Our in situ study revealed that the Eley–Rideal mechanism prevailed. We could also follow the gradual decay of the catalytic activity, and its regeneration; this was the first reported study to do so in quantitative detail. The preparation technique described herein is now extensively used by others. I am told that this paper is the most cited of all papers on heterogeneous catalysis published by Nature.
10.1038/378159a0
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3“Design of a ‘green’ one-step catalytic production of ε-caprolactam (precursor of nylon-6)”: J. M. Thomas, R. Raja, Proc. Natl. Acad. Sci. 2005, 102, 13732–13736. This is a laboratory-based proof of principle that a benign solvent-free method exists (using air and ammonia in place of aggressive reagents, i.e., oleum and hydroxylammonium sulfate) for the production of ε-caprolactam. Moreover, there are no nasty by-products. In contrast, the favored industrial method forms almost four times as much ammonium sulfate as it does nylon-6. The latter product is formed by simply heating ε-caprolactam. It is readily recyclable, unlike nylon-6,6.
10.1073/pnas.0506907102
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4“Mechanistic Insights into the Conversion of Cyclohexene to Adipic Acid by H₂O₂ in the Presence of a TAPO-5 Catalyst”: S.-O. Lee, R. Raja, K. D. M. Harris, J. M. Thomas, B. F. G Johnson, G. Sankar, Angew. Chem. 2003, 115, 1558–1561;
10.1002/ange.200250351
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Angew. Chem. Int. Ed. 2003, 42, 1520–1523. When a Ti^IV ion is incorporated into the framework of ALPO-5, it confers not only Lewis acidity but weak Brønsted acid activity to the catalyst. This bifunctionality makes it possible to carry out a cascade of catalyzed reactions in “one pot”. Cyclohexene can now be routinely prepared (thanks to Japanese industry) from benzene. We set out (with Kenneth Harris) to investigate, using parallel ¹³C and ¹H NMR and GC-MS analysis, the course of the benign conversion of the hexene to adipic acid, and were able to identify seven distinct intermediates, one of which (the cis diol, but not the trans diol), to our surprise, is formed by a free-radical mechanism.
10.1002/anie.200250351
CAS PubMed Web of Science® Google Scholar
5“Sheet Silicates: Broad Spectrum Catalysts for Organic Synthesis”: J. A. Ballantine, J. H. Purnell, J. M. Thomas, J. Mol. Catal. 1984, 27, 157–167. This paper describes the strategy and details of how, using acidic, synthetic montmorillonites, or beidellites, one may catalytically prepare a wide range of solvents and building blocks for fine chemicals, active pharmaceutical ingredients, and heavy chemicals (ethers, esters, amines, alcohols, and alkylated arenes). In particular, we outlined a one-step, solvent-free, 100 % atom-efficient synthesis of ethyl acetate that involves the interlamellar addition of acetic acid to ethylene over our new solid-acid catalysts. A variant of this (patented) discovery is now the basis of the “green” industrial synthesis of ethyl acetate, on a 300 000 tonnes per annum scale in the UK.
10.1016/0304-5102(84)85077-4
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Volume52, Issue42

October 11, 2013

Pages 10938-10940

Sir John Meurig Thomas

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