Editor's Page pubs.acs.org/Organometallics
Editorial: An Award-Winning Tutorial
T
again critical, with subtle changes in substitution of the cyclopentadienyl rings having a profound influence on the outcome of the chemistryan effect thoroughly appreciated by my laboratory!3 The second is the preparation of organometallic compounds in new oxidation states. Perhaps there is no topic more venerated in the minds of organometallic chemists than formal oxidation state assignment.4,5 In the 21st century, it is hard to imagine that examples of organometallic compounds in previously unobserved oxidation states are still possible to discover. Evans and co-workers did just that. The Tutorial describes the discovery of the first molecular compounds of Ho2+ and the later examples that follow. From a historical perspective, it is remarkable that appropriately substituted tris(cyclopentadienyl) derivatives serve as the synthetic entry point to these compounds. Organolanthanide chemistry traces its origins to Wilkinson and Birmingham’s synthesis of (η5-C5H5)3Ln over 60 years ago,6,7 demonstrating that cyclopentadienyl ligands are still vibrant sources of new chemistry even after six decades. I hope readers, particularly students, appreciate how fundamental questions can produce such transformative chemistry. This Tutorial reminds us that we still have much to learn about the periodic table and, most importantly, that organolanthanide chemistry is a source of much excitement and a fertile area for growth in organometallic chemistry. I want to close by thanking Bill Evans for an outstanding contribution to Organometallics and congratulating him on his ACS national award.
he lanthanides are often forgotten elements on the periodic table. In high school chemistry, I was required to learn the names and atomic symbols of all of the elements except for the lanthanides and actinides. Unfortunately, the same is often true in organometallic chemistry courses. The chemistry of d-block transition metals is emphasized at the expense of the lanthanides. This viewpoint is, of course, shortsighted and the Tutorial in this issue written by Professor Bill Evans at the University of CaliforniaIrvine will hopefully remind readers that the organometallic chemistry of the later, heavier elements is rich and exciting and is still providing many new surprises, including underexplored oxidation states. Professor Bill Evans is no stranger to the readers of Organometallics, having contributed nearly 100 papers to the journal since 1983. Bill was recently named a Distinguished Professor by the University of California, and his work is synonymous with the organometallic and coordination chemistry of the rare earths and the actinides. Having trained as a graduate student with M. Frederick Hawthorne at UCLA working on metallocarborane chemistry and later as a postdoctoral associate at Cornell University with Earl Muetterties studying phosphite ligands, he admirably ventured into uncharted waters when he began his independent career at the University of Chicago. His landmark papers1,2 on the synthesis and later structural characterization of decamethylsamarocene, (η5-C5Me5)2Sm, much like the discovery and structural identification of ferrocene, ushered in a new era of organometallic chemistry. Much in the spirit of Sir Geoffrey Wilkinson, Bill and his research group have marched across the lanthanide series, exploring the chemistry of lanthanide cyclopentadienyl compounds. For these discoveries, Bill has been recognized with many awards. Most notably, he received the 2005 ACS Award in Inorganic Chemistry and the 2015 ACS Award in Organometallic Chemistry. It is this latter recognition and associated award lecture that served as the inspiration for Bill’s Tutorial. The paper embodies the spirit of the Tutorial, offering an accessible and focused introduction to the traditional organometallic chemistry of the lanthanides and nimbly moving to contemporary problems and challenges with the chemistry of reduced rare earths. The story integrates the central role that ligand design and metal complex synthesis continue to play in our field. Readers be warned thoughthe Evans group makes this chemistry look easy. As someone who continues to work in the area of reduced earlytransition-metal cyclopentadienyl chemistry, I can assure readers it is not. Compounds of this type are often extremely air sensitive, oxophilic, highly reactive, and in some cases thermally unstable. Some of these intricacies are highlighted in the Tutorial, and the accompanying illustrations of how the compounds are prepared give the reader an idea of the level of effort and technical expertise required to successfully execute this chemistry. There are many striking aspects of the Tutorial, but I will highlight just two. The first is the preparation of dinitrogen complexes of many of the rare-earth elements. Ligand design is © XXXX American Chemical Society
Paul J. Chirik
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Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
AUTHOR INFORMATION
Notes
Views expressed in this editorial are those of the author and not necessarily the views of the ACS.
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REFERENCES
(1) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. J. Am. Chem. Soc. 1981, 103, 6507. (2) Evans, W. J.; Hughes, L. A.; Hanusa, T. P. J. Am. Chem. Soc. 1984, 106, 4270. (3) Pool, J. A.; Lobkovsky, E.; Chirik, P. J. Nature 2004, 427, 527. (4) Parkin, G. J. Chem. Educ. 2006, 83, 791. (5) Green, M. L. H. J. Organomet. Chem. 1995, 500, 127. (6) Wilkinson, G.; Birmingham, J. M. J. Am. Chem. Soc. 1954, 76, 6210. (7) Birmingham, J. M.; Wilkinson, G. J. Am. Chem. Soc. 1956, 78, 42.
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DOI: 10.1021/acs.organomet.6b00708 Organometallics XXXX, XXX, XXX−XXX
