Reactivity and Functionalization of Naphthalene and Anthracene Complexes of {TpW(NO)(PMe3)}

Strausberg, Laura, Chemistry - Graduate School of Arts and Sciences, University of Virginia
Harman, Walter, Department of Chemistry, University of Virginia

Chapter 1 introduces the organic chemistry of aromatic hydrocarbons, with attention paid to regiochemical outcomes of organic reactions. The binding of naphthalene and anthracene to metal complexes is discussed, along with organic transformations they undergo as a result of their complexation. The previous work on osmium and rhenium complexes of naphthalene from the Harman group is explored. Finally, some spectroscopic techniques for exploring the chemistry of {TpW(NO)(PMe3)} complexes of naphthalene and anthracene are introduced.
Chapter 2 discusses the highly distorted allyl complexes formed from {TpW(NO)(PMe3)} and the exploration of their origin. Attempts at stereoselectively deprotonating these cationic complexes is also discussed.
Chapter 3 describes our study of TpW(NO)(PMe3)(3,4-η2-naphthalene)’s ability to undergo a Diels-Alder reaction with N-methylmaleimide. A solvent study suggested that this reaction proceeds by a concerted mechanism. To probe the mechanism further, we synthesized a series of methylated and methoxylated naphthalene complexes and measured their rates of reaction with N-methylmaleimide compared to the parent complex. We found that 1-substitution on the naphthalene increased the rate of cycloaddition, even if the substituent was in the unbound ring, while 2-substitution slowed the reaction rate when in the bound ring. This information is consistent with a concerted mechanism, as a 2-substituted product would be less able to isomerize to form the active isomer for the cycloaddition to occur.
Chapter 4 discusses tandem electrophile and nucleophile additions to TpW(NO)(PMe3)(3,4-η2-naphthalene) and TpW(NO)(PMe3)(3,4-η2-anthracene), where the electrophile is not carbon-based. Addition of a proton to each complex yields a complex that undergoes Friedel-Crafts-type additions to aromatic nucleophiles. Decomplexation conditions were developed for several of these. TpW(NO)(PMe3)(3,4-η2-anthracene) also reacts with N-bromosuccinimide to yield a cationic species to which a variety of nucleophiles added. Loss of bromide allows for addition of a second equivalent of nucleophile.
Chapter 5 discusses reactions of carbon electrophiles with the naphthalene and anthracene complexes. TpW(NO)(PMe3)(3,4-η2-anthracene) reacts with acetal reagents to generate cationic ylidene species. Nucleophiles could be added to both C2 on the anthracene ring and to the benzyl carbon, depending on the nucleophile. Decomplexation conditions were developed for several complexes, including 1-substituted anthracenes. Attempts a oxidizing a substituted anthracene to anthraquinone is briefly addressed.
Chapter 6 considers the implications of the work described here on generating new functional molecules from aromatic hydrocarbons.

PHD (Doctor of Philosophy)
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