Synthesis and characterization of group-13-bridged [1]- and [1.1]metallacyclophanes

The synthesis and characterization of the first aluminum- and gallium-bridged [1]chromarenophanes, [1]vanadarenophanes and [1]molybdarenophanes are described; these compounds belong to a class of compounds referred to as [1]metallacyclophanes. [1]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 [1]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 [1]molybdarenophane undergoes ring-opening reactions catalyzed by sigma donors such as thf and PEt3 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 [1]metallarenophanes, possibly due to steric overprotection.;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 [1]metallarenophanes, some generalizations can be made. For a given [1]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 [1]metallarenophanes, which can be attributed directly to their respective metallic radii.;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.