[Cp*Rh] Monohydrides Supported by Diphosphine Ligands: Synthesis, Characterization, and Multifrequency Nuclear Magnetic Resonance Studies

Abstract

The ability of ligands to influence the stability, spectral properties, and reactivity of transition metal complexes is a broadly well-developed area of inorganic chemistry. Likewise, the importance of developing new methodology for the transformation of small organic molecules is an area of importance within organic chemistry. Part I of this dissertation, consisting of Chapters 1, 2, and 3, contains the core research contributions of this dissertation, performed on the [Cp*Rh] platform. The introduction in Chapter 1 of this dissertation provides a comprehensive overview of the research findings of the Blakemore Group on the [Cp*Rh] system. Chapters 2 and 3 of this dissertation, the context of which is outlined in Chapter 1, describe the bookend preparative study by our group on this system, including the synthetic, spectral, and reactivity properties of [Cp*Rh] complexes supported by two different diphosphine ligands. This analysis includes multifrequency NMR characterization (400–800 MHz) as well as digital NMR simulations to probe the rich coupling networks present in two cases. Part II consists of a collection of self-contained projects which were also completed. Chapter 4 describes a catalytic hydrogenation study for a series of heterobimetallic complexes of [Cp*Rh] previously prepared by our group. It was found that the catalysis of these complexes was modest, at best, toward hydrogenation of a benzaldehyde compound. Chapter 5 describes the development of a new C–N bond-forming transformation which utilizes benzoquinones as mediators for an annulation reaction. This work was serendipitously discovered through the formation of an undesired indole byproduct in prior work; this discovery led to the optimization and scope study of the chemistry to provide N-arylindoles and N-arylpyrroles. Chapter 6 describes the preparation of a series of four polypyridyldicarboxylic acids for use in coordination of the uranyl dication; two of these ligands were bipyridyl-based while the other two were terpyridyl-based. The ligands showed great promise for the formation of uranyl coordination complexes; however, solubility issues impeded detailed characterization and spectral analysis. Finally, Chapter 7 consists of a collection of preliminary attempts to develop conditions for asymmetric, dual-catalytic, decarboxylative elimination of carboxylic acid substrates under photoredox conditions. Taken together, the work described in Parts I and II of this dissertation contribute to the areas of organic, organometallic, and f-element chemistry.