The Reactivity of eta-2-Aminoarenes Coordinated to Tungsten via Acid Trapping

Pienkos, Jared, Chemistry - Graduate School of Arts and Sciences, University of Virginia
Harman, Walter, Department of Chemistry, University of Virginia

The Reactivity of η2-Aminoarenes Coordinated to Tungsten via Acid Trapping

(Under the direction of Professor W. Dean Harman)

The Harman lab exploits π-basic metal fragments to functionalize arenes. Coordination of an aromatic molecule to a π-basic metal fragment usually occurs in an η2-fashion. In the process of complexation, the arenes are dearomatized, and the resulting ligands are able to undergo synthetic transformations that are inaccessible to the unbound, organic analogs.(1) Currently, the [TpW(NO)(PMe3)] metal fragment is used as a dearomatization reagent because of its low cost, scalability, and accessibility to a TpW(NO)(PMe3)(η2-benzene) complex. The η2-coordinated benzene can be substituted with a variety of aromatic ligands.(2)

For example, an aromatic ring with an amine moiety can be exchanged with tungsten-bound benzene and protonated in situ, forming its conjugate acid. This product, although cationic, is able to undergo a second electrophilic addition. Modifications of these bound arenes result in the formation of novel organometallic derivatives.

Friedel-Crafts, (3) hydroamination, and cyclopropanation (4) reactions have been performed on these coordinated η2-aminoarenes. In some cases, after synthetic modifications, the functionalized ligand can be removed from the metal fragment. This strategy has been used to generate cyclohexenone, amidine, and hexahydroindole derivatives.

(1) Keane, J. M.; Harman, W. D. Organometallics 2005, 24, 1786.

(2) Welch, K. D.; Harrison, D. P.; Lis, E. C.; Liu, W.; Salomon, R. J.; Harman, W. D.; Myers, W. H. Organometallics 2007, 26, 2791.

(3) Pienkos, J. A.; Zottig, V. E.; Iovan, D. A.; Li, M.; Harrison, D. P.; Sabat, M.; Salomon, R. J.; Strausberg, L.; Teran, V. A.; Myers, W. H.; Harman, W. D. Organometallics 2013, 32, 691.

(4) Pienkos, J. A.; Knisely, A. T.; Liebov, B. K.; Teran, V.; Zottig, V. E.; Sabat, M.; Myers, W. H.; Harman, W. D. Organometallics 2013, 33, 267.

PHD (Doctor of Philosophy)
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