Organoaluminum Complexes Incorporating Redox-Active Ligands

10 Organoaluminum Complexes Incorporating Redox-Active Ligands 

The first redox-active and paramagnetic complex of Al(lll) to be reported was Al(bpy)3 (bpy = 2,2 -bipyridyl) and was prepared by the reduction of AICI3 with Li(bpy) [252]. Based on magnetic measurements, the product species was proposed to be best described as containing an Al cation, with the unpaired electrons being extensively delocalized on the bpy ligands. More recently, related radical anion complexes of tris(l,3-diphenyltriazenido)aluminum have been isolated and structurally characterized [253]. Nax[Al(dpt)3] complexes were prepared by the stoichiometric reduction of Al(dpt)3 by Na in THF (Eq. 22). 

Surprisingly, redox chemistry involving Al(lll) species supported by quinones and other O-donor non-innocent ligands remains in its infancy since early studies on the reaction of alkylaluminum dichlorides with 1,4-quinones for the production of aryl ethers via a radical-radical coupling process [270-272]. 

While redox chemistry of metal complexes typically takes place at the metal center, the use of metal species bearing so-called redox non-innocent ligands may promote a metal/ligand cooperation in a synergistic manner. Therefore such complexes offer interesting prospects for uncovering unprecedented stoichiometric 

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