Fundamental Reactions of Coordinated Ligands

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This award in the Inorganic, Bioinorganic, and Organometallic Chemistry program provides continued support for studies of fundamental reactions of coordinated ligands by Dr. Joseph L. Templeton, Department of Chemistry, University of North Carolina at Chapel Hill. Research will be carried out in three areas all involving the synthesis of organometallic complexes utilizing the tridentate hydridotris(3,5-dimethylpyrazolyl)borate ligand, Tp'. The strategy for each area is to explore fundamental reactivity patterns of coordinated substrate ligands. The first area extends the chemistry of chiral d4 complexes of tungsten previously shown to successfully control stereochemistry at ligand beta-sites. A cationic methylene carbene complex will be used for stoichiometric and catalytic reaction studies of substrate ligands. For example, catalytic aziridine formation occurs by reaction of ethyl diazoacetate with imine adducts. Single enantiomer studies will be pursued. The second and main area of the project involves the use of a new high oxidation state d2 tungsten oxo system which simultaneously accommodates both pi-acid and pi-base ligands. New d2 tungsten complexes should yield chiral organometallic derivatives that contain sigma or pi bound organic ligands. Preliminary results show interesting and different reactivities such as ligand coupling reactions (C-C bond formation) and proton addition at the oxo group converting W=O to W-OH, a rare example of an organometallic terminal hydroxo ligand. These reactions will be extended to seek catalytic transfer of nitrene and carbene ligands and to generate chiral d2 complexes suitable for promoting Lewis acid assisted organic transformations. The third area involves the preparation of chiral Tp' derivatives of Pt(IV) from known hydrido complexes in order to generate vacant sites for electrophilic activation of organic substrates. This work has potential for great impact because it may give insight into how C-H bond activation reactions work in electrophilic, late transition metal complexes. This project will increase our fundamental knowledge of transition metal mediated reactions of organic substrates. In addition, these and related compounds may have applications in promoting or catalyzing important organic transformations, including ones of interest to the chemical and pharmaceutical industries.