Organometallics 2009, 28, 4235–4235 DOI: 10.1021/om900523n
4235
Introduction to the Review by A. J. Ashe III in This Issue of Organometallics The formal replacement of a CH ring member of a cyclic aromatic hydrocarbon by a BHgroup has provided new classes of organoboron ligands for use in the preparation of transition-metal complexes. Thus, there is Gerhard Herberich’s pioneering work on boratabenzenes, in which a CH group of the benzene ring has been replaced by a BRgroup to give the [C5H5BR]- anions. These have found application as π ligands in the preparation of many new transition complexes, of which [η-C5H5BNPri2]2ZrCl2 is an example. The review in this issue of Organometallics by Arthur J. Ashe III of the University of Michigan covers related transition-metal complexes that contain five-membered cyclic ligands prepared by a similar BH- for CH replacement strategy in thiophene, furan, and pyrrole, as well as the six-membered [1,2-RBNC4H4]- analogue of pyridine. Our two cover figures, 1 and 2, [η5-C5Me5]Ru complexes that contain thiophene analogues, the 1,3- and 1,2-thiaborolyl rings, respectively, show that ring isomeric ligands can be prepared. The 1,3isomer, a red crystalline solid, mp 82-84 °C, was reported in 1991 (Ashe, A. J., III; Fang, X.; Kampf, J. W. Organometallics 1999, 18, 1821) and the 1,2-isomer, amber crystals, mp 84 °C, a year later (Ashe, A. J., III; Fang, X.; Kampf, J. W. Organometallics 2000, 19, 4935). Professor Ashe has done an excellent job of summarizing the preparation and studies of such boron-containing heterocyclic ligands (which involves novel organoboron chemistry) and of their transition-metal complexes.
Professor Ashe carried out all of his studies in chemistry at Yale University (B.A. 1962, Ph.D. 1966, dissertation research with K.B. Wiberg), with a year (1962-1963) spent at the University of Cambridge with F. G. Mann. He has been a member of the chemistry department faculty of the University of Michigan since 1966 (full professor since 1976, professor emeritus in 2008). Professor Ashe’s research career has been devoted for the most part to the synthesis and detailed study of interesting heterocyclic compounds containing group 13 and 15 element atoms as ring members. A signal achievement, for which he received national and international recognition early in his career, was the first syntheses of the aromatic heterocycles phosphabenzene, arsabenzene, and stibabenzene, in which a group 15 atom has replaced a CH group of benzene. Over the years these compounds, as well as bismabenzene, a later arrival, have been the subjects of broad and detailed physical and spectroscopic studies aimed at obtaining a detailed understanding of the bonding in these molecules. Later research in Professor Ashe’s laboratory extended this work to the preparation of their transition-metal complexes. Professor Ashe’s interest in boron-containing heterocycles also began early with a publication in 1971 on the 1-phenylborabenzene anion, but work in this area was put on the back burner while he developed the group 15 element containing heterocycles. The preparation in 1987 of the new aromatic organoboron compound 1-methyl-4,5-cyclopentenoborepin, a neutral boron-containing analogue of the tropylium ion, established a new area of research for Professor Ashe and led to the preparation of transition-metal complexes such as 1-phenylborepinmolybdenum tricarbonyl. Noteworthy was his synthesis of the first aromatic gallium heterocycle, gallatabenzene, in 1995. In 1997 the studies devoted to the synthesis of the boron-containing heterocycles that are the subject of Professor Ashe’s review began in earnest. Professor Ashe’s research from the start has involved outstanding synthetic chemistry; original, innovative, and elegant, aimed at subjects of fundamental interest and importance, very thorough in breadth and depth. As a result, his impact on the areas in which he has carried out research has been significant and lasting. As usual, I am grateful to Professor Arnold L. Rheingold for the cover figures.
Dietmar Seyferth Editor
r 2009 American Chemical Society
Published on Web 07/06/2009
pubs.acs.org/Organometallics
