UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

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Author: search.filters.author.Mayo, Dennis Hansel

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    Synthesis and Characterization of Low-Valent Aluminum and Gallium Compounds from Aluminum (I) and Gallium (I) Precursors
    (2011) Mayo, Dennis Hansel; Eichhorn, Bryan W; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In this thesis the design, assembly, and operation of a metal halide co- condensation reactor capable of generating metastable solutions of aluminum and gallium monohalides is described. In this reactor, gas-phase molecules are co-condensed with a mixed solvent at 77 K and the resultant metastable solutions are stored at 198 K. Upon warming, these solutions undergo disproportionation reactions to form metalloid cluster compounds. The optimization of multiple reactor settings for monohalide generation is described. The efficacy of the reactor was validated by reproducing the synthesis of large clusters of Ga and Al; namely [Al77(NTMS2)20]2- and [Ga12Br2(GaBrNTMS2)10]2- which were first described by Schnockel et al. In order to better understand the challenges of low-valent aluminum and gallium chemistry a comprehensive literature review is presented. This review describes the synthetic pathways by which low-valent aluminum and gallium compounds are prepared, as well as in-depth discussion of structural and spectroscopic properties of these compounds. Two new low oxidation state Al3 clusters have been prepared by the reaction of lithium phosphides with metastable AlCl*Et2O. Both of these compounds have the general formula Li2[Al3(PR2)6]*2 Et2O (where R = C6H5 or C6H11) and formally contain Al+1.3 ions . These compounds have been characterized by X-ray diffraction and their paramagnetic nature probed by 1H NMR (Evans method) and EPR spectroscopy. The aluminum hydride cluster [Al3H6]2- has been modeled by DFT calculations (6-31G*, Hyperchem) to visualize the molecular orbitals in the [Al3(PR)6]2- clusters. The preparation of three novel aluminum (III) amidinate compounds is described. These compounds (Al(PhC(NiPr)2)3, Al(PhC(NiPr)2)2Cl, and Al(PhC(NCy)2)2Cl) are formed as the result of ligand-exchange and disproportionation processes that occur during the reaction of lithium amidinates with metastable AlCl*Et2O. The synthesis of the gallium dimer Ga2Br4*2 PHCy2 is also described.