Synthesis and Characterization of Group-13-Bridged - and [1.1]Metallacyclophanes
Lund, Clinton Laine
The synthesis and characterization of the first aluminum- and gallium-bridged chromarenophanes, vanadarenophanes and molybdarenophanes are described; these compounds belong to a class of compounds referred to as metallacyclophanes. Metallacyclophanes are strained, ring-tilted complexes that have a propensity to undergo ring-opening polymerizations (ROPs). On the basis of using bulky, intramolecularly coordinating ligands, the metallacyclophanes described within have been synthesized and characterized. By exploring known transition-metal catalyzed ROP methodologies, a serendipitous discovery has been made. The gallium-bridged molybdarenophane undergoes ring-opening reactions catalyzed by sigma donors such as thf and triethylphospine or by pi donors such as 1,5-cyclooctadiene. Known transition-metal catalyzed ROP methodologies proved to be unsuccessful with the aluminum- and gallium-bridged metallarenophanes, possibly due to steric overprotection. The synthesis and characterization of the first [1.1]metallarenophanes is described. By utilizing ligands with dimethylamine-donor functionalities, aluminum- and gallium-bridged unstrained [1.1]chromarenophanes and [1.1]molybdarenophanes have been isolated. Gallium-bridged [1.1]metallarenophanes have been determined to be Class II compounds through investigations by cyclic voltammetry. Aluminum-bridged [1.1]metallarenophanes can not be successfully characterized by electrochemical measurements because of their acute sensitivity towards oxygen and moisture. All isolated [1.1]metallarenophanes adopt anti conformations in the solid state. Several new reactive aluminum, gallium and indium and compounds have been prepared that incorporate bulky donor ligands. All new compounds have been characterized by NMR spectroscopy, X-ray crystallography, mass spectrometry and elemental analysis. When comparing solid-state structures of metallarenophanes, some generalizations can be made. For a given metallarenophane gallium-bridged compounds are always more tilted when compared to their respective aluminum-bridged compound for reasons that still remain unknown. If the bridging element is kept constant, the tilt angles are found to increase in the order of Mo > V > Cr for the metallarenophanes, which can be attributed directly to their respective metallic radii.
DegreeDoctor of Philosophy (Ph.D.)
CommitteeUrquhart, S. G.; Majewski, M.; Moewes, A.; Macdonald, C.; Foley, S. R.