Dr. Dwight A. Sweigart, Department of Chemistry, Brown University, is supported by the Inorganic, Bioinorganic, and Organometallic Program of the Chemistry Division for the study of chemical reactions effected by the coordination of the manganese tricarbonyl moiety to aromatic ligands and for the development of systems that contain a redox switch to activate or deactivate remote metal centers. The ability of coordinated manganese tricarbonyl fragments to activate aromatic ligands will be exploited to prepare a wide range of monoarenes and heterocycles. Examples include functionalized centropolyindan hydrocarbons and stereoselectively derivatized prochiral arenes. Arene ligand exchange will be extended to bimetallic complexes of conjugated polyarenes containing a variety of metals. Concentrating on hydroquinone and catechol complexes, the redox properties of the metals will be evaluated. The studies will converge into the design of systems in which metal-metal interactions can be electrochemically switched on or off. Drawing on the reactivity of the manganese tricarbonyl fragment, reductive insertion reactions into sulfur-carbon bonds will be developed, with an emphasis on processes related to HDN and HDS. This project will concentrate on developing several applications for manganese metal complexes. The first of these aims at the synthesis of selected types of organic molecules and at the use of manganese containing species to break carbon-sulfur bonds in thiophenes. This study is significant because the removal of thiophenic materials is important to the desulfurization of fossil fuels and manganese is especially attractive for this application because of its low toxicity and relative abundance. Another major activity is the development of systems in which the transfer of an electron to or from a metal atom will control the behavior of a second metal center. This will have relevance to several areas including the control of conductivity and optical properties in metal containing materials.
