Chemistry & Biochemistry Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2752

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    ELECTRONIC MODIFICATION WITHIN THE WELL-ESTABLISHED CPAM FRAMEWORK AS A MEANS TOWARD INCREASED REACTIVITY
    (2017) Thompson, Richard; Sita, Lawrence R.; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Early transition metals (group IV-VI) supported by the pentamethylcyclopentadienyl-amidinate mixed ligand set (CPAM) have been found to enable a number of important chemical transformations including (living) coordinative polymerization of alpha-olefins, fixation of dinitrogen and group transfer chemistry involving oxo, imido and sulfido ligands to unsaturated organic substrates, including carbon dioxide. A great deal of the allure and success associated with these complexes is their modularity, particularly as it concerns the amidinate component which is tunable at both the N-bound substituents as well as the distal position. Accordingly, a great deal of work has established that by reducing the sterics in all three positions engendered higher reactivity. There exists, however, a practical “steric wall” such that the size of substituents can only be contracted so much. Tuning of the electronic character of these well-established systems could prove to be a novel and potent method for affecting reactivity of these complexes within an already well understood steric environment.
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    REDUCTIVE ELIMINATION OF (DPMS)PTIV COMPLEXES DERIVED FROM ISOMERIC 2-BUTENEs AND 2-BUTYNE (DPMS=DI(2-PYRIDYL)METHANE SULFONATE)
    (2012) Liu, Xiaohang; Vedernikov, Andrei; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The (dpms)PtII complexes (dpms = di(2-pyridinyl)methanesulfonate)derived from some cyclic olefins can be readily oxidized to PtIV oxetanes, followed by reductive elimination to produce corresponding epoxides. A catalytic version of this reaction can potentially be achieved if decomposition of active species responsible for olefin substitution is avoided. Several attempts were made to solve this problem, and a more hydrophilic analog of the dipyridinemethanesulfonate ligand was obtained. Furthermore, the reductive elimination step of PtIV oxetanes was studied by using diastereomeric cis- and trans-2-butene derivatives. We believe that two mechanisms of C O reductive elimination may be involved in these reactions and that steric repulsion between substituents at the oxetane carbon atoms may play a major role in determining the predominant of the two competing mechanisms. Platinum(IV) η1-butanone complex was synthesized and characterized, which was found to undergo different types of elimination reaction to give a series of butane derivatives as products.