Organic Transformations of Coordinated Ligands

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The focus of this project in the Inorganic, Bioinorganic and Organometallic Chemistry Program is chemical transformations of organic molecules which occur while these molecules are bound to a metal. These reactions are intimately related to reactions of organic chemicals which occur on homogeneous or heterogeneous transition metal catalysts, and include some of the most important reactons in industrial chemistry. Alkyne ligands and eta-2-allenyl ligands are isolobal and constitute a conjugate acid-base pair. The deprotonation/alkyl- ation reaction sequence which is central to enolate chemistry can be duplicated with metal bound 4-electron donor alkyne ligands bearing a beta-hydrogen. Deprotonation at the beta carbon of the alkyne forms a nucleophilic eta-2-allenyl ligand suitable for electrophilic addition and aldol type condensation reactions at the beta carbon. The use of the metal fragment to provide both regio and stereocontrol in such reactions will be explored. Also to be investigated is the possibility that the formation of a gamma alcohol by aldehyde addition to the allenyl could lead to elimination to form a conjugated enyne bound through the alkyne triple bond and poised for 1,4-conjugate addition reactions. Release of the functionalized alkyne is expected to provide a powerful vehicle for building diverse organic building blocks. Since eta-2-iminoacyl and eta-2-vinyl ligands are expected to be acidic at the beta carbon position also, elaboration of these ligands via nucleophilic coordinated anion and eta-2-allene intermediates, respectively, will be pursued. Following on the successful stepwise reduction of metal bound nitriles by successive hydride addition and protonation reactions, diastereoselective nitrile reductions will be attempted, and the retention of configuration at the metal center will be probed in an effort to develop a catalyst for chiral amine syntheses.