Exploring the Multi-valency of Dirhodium Carboxamidates: From Catalytic Mechanisms of Oxidation to Materials Applications

University Of Maryland, College Park, College Park MD

Investigators

Abstract

With this award from the Organic and Macromolecular Chemistry Program, Prof. Michael Doyle will focus on two fundamental discoveries in the chemistry of metal compounds that have exciting potential for revolutionary developments in chemistry. The first is chemical oxidations of organic compounds by inexpensive tert-butyl hydroperoxide (70% in water) using these metal compounds. The second is based on their discovery of a new class of metal-containing organic compounds that show high potential as new and unexplored materials. Both are related to the unique ability of rhodium to bind to a second rhodium when connected to amide structures that bridge the two rhodium atoms. The compounds that result have two rhodium atoms connected to four amide structures in the form of a paddlewheel, and their unique properties include an ability to be oxidized with low input of energy. Encouraged by results in catalytic oxidations by tert-butyl hydroperoxide that reveal significant advantages for their strategy over alternative catalytic strategies, among which are (1) low catalyst loading (down to 0.1 mol %) to achieve high product yields, (2) formation of ketones selectively in a variety of organic compounds, and (3) reactions occur in water without destruction of catalyst, they will develop a broad understanding of these oxidative processes. They will determine the specific pathway or pathways for oxidation, as well as methods to direct the reaction to a specific pathway, so that applications can be broadened to oxidations of complex organic compounds that include steroids and unsaturated fatty acids. The discovery of rhodium-containing organic compounds that have structural rigidity, stability, and design flexibility, and a general methodology for their preparation, has made possible the construction of previously unknown organometallic materials. Because these materials do not have a metal-metal bond, they are potentially good insulators; the group will focus on the production of molecular wires with these compounds with efforts to achieve conductance through electron transfer so that, as insulators and conductors, they may be able to develop molecular switches. Broader Impacts. The implications of this research promise new insights into the interception of radical intermediates and control of reaction pathways for product formation, many of which are related to biological processes. The compounds that they prepare by mild methods provide a broader selection of effective catalysts in carbon-carbon bond forming reactions. Rhodium-containing organic compounds are a new class of easily accessed organometallic materials whose function could be of benefit in electronics or optics, as well in the development of new polymeric substances. The variety of education and training afforded by this research benefits postdoctoral, graduate student and undergraduate student participants.