METALLOCENOPHANES AND METALLOPOLYMERS WITH ALUMINUM, GALLIUM, SILICON, AND TIN IN BRIDGING POSITIONS
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Three new aluminum and gallium dichlorides equipped with the ligands Pytsi-SiMe2 [Pytsi-SiMe2 = -C(SiMe3)2(C6H4N-2)], Pytsi-2SiMe3 [Pytsi-2SiMe3 = -CH2(SiMe2C6H4N-2)], and Mx (Mx = 4,6-di-tBu2-2-Me2N-C6H3) were synthesized and fully characterized. (Mx)GaBrxCl2-x was isolated after a chlorine-bromine exchange that can be triggered by LiBr. Moreover, the stereoselective formation of rac-(Pytsi-2SiMe2)2AlMe and rac-(Pytsi-2SiMe2)2AlCl [Pytsi-2SiMe2 = -C(SiMe3)Me(C6H4N-2)] was found. Salt-metathesis reactions between aluminum or gallium dihalides decorated with the Pytsi-SiMe2 ligand and 1,1'-dilithioferrocene gave rise to aluminum- and gallium-bridged ferrocenophanes (FCPs). However, these FCPs were not isolated, because they underwent ring-opening polymerization to yield low-molecular-weight polymers. When the Mx ligand was employed in salt-metathesis reactions with 1,1'-dilithioferrocene or 1,1'-dilithioruthenocene, metallopolymers were obtained as major products and aluminum- and gallium-bridged [1.1]FCPs were obtained as minor products. The formation of gallium-bridged metallocenophanes that were consumed by ring-opening polymerization was observed. In the case of the Pytsi-2SiMe3 ligand, salt-metathesis reactions yielded an inseparable mixture of aluminum- and gallium-bridged [1.1]FCPs and oligomers. (Pytsi-2SiMe3)AlCl2 and (Pytsi-2SiMe3)GaCl2 were then reacted with lithioferrocene to give bis(ferrocenyl) compounds. The bis(ferrocenyl)aluminum and gallium compounds were fully characterized and electrochemically studied. The different outcome of the salt-metathesis reactions can be rationalized by the different steric bulk of the employed ligands. The first examples of [1.1]FCPs with different bridging elements and polyferrocenes with alternating bridging elements containing combinations of silicon-tin and silicon-gallium were synthesized and characterized. When silicon and tin were used as bridging elements, [1.1]FCPs were only formed as minor products in a mixture with other linear and cyclic polyferrocenes. A [184.108.40.206]FCP with alternating tin and silicon bridges was isolated and fully characterized and showed an interesting redox behavior. The gallium- and silicon-bridged [1.1]FCP was obtained as the major product and fully characterized including single-crystal X-ray analysis and cyclic voltammetry. The first aluminum- as well as gallium-bridged [1.1]ruthenocenophanes ([1.1]RCPs) were synthesized and fully characterized. The solid-state structure of the gallium-bridged [1.1]RCP was similar to the respective [1.1]FCP. Electrochemical study of both species revealed two electrochemically irreversible oxidation waves. These properties contrast those of the methylene-bridged [1.1]RCP, the only [1.1]RCPs that was studied previously by single-crystal X-ray analysis and electrochemistry.
DegreeDoctor of Philosophy (Ph.D.)
CommitteeFoley, Stephen R.; Dimmock, Jonathan R.
Copyright DateOctober 2012
ferrocenophanes ruthenocenophanes metallopolymers aluminum gallium