Synthesis and ε-Caprolactone Polymerization Activity of Electron-Deficient Gallium and Aluminum Species Containing a Charged Redox-Active dpp-Bian Ligand.

The synthesis of electron-deficient gallium- and aluminum-centered species containing a redox-active dpp-Bian ligand (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) is described. The reaction of digallane [(dpp-Bian)Ga-Ga(dpp-Bian)] with [PhC][PF] or AgPF resulted in polyoxidized species [(dpp-Bian)GaF] (), [(dpp-Bian)H][PF] (), and [(dpp-Bian)GaF(OPF)] (). The reaction of digallane with B(CF) led to electron-deficient gallylene [(dpp-Bian)GaB(CF)] of a dpp-Bian radical anion. The soft oxidation of digallane with tosyl cyanide gave the trinuclear cationic species [(dpp-Bian)Ga(Tos)Ga(Tos)Ga(dpp-Bian)][Ga(CN)] () containing dpp-Bian radical anions. The reaction of [(dpp-Bian)AlEt] with 1 equiv of [PhC][B(CF)] resulted in the cationic complex [(dpp-Bian)AlEt][B(CF)] () of neutral dpp-Bian, while the treatment of [(dpp-Bian)AlEt(EtO)] with 1 equiv of [PhC][B(CF)] resulted in the compound [(dpp-Bian)AlEt(EtO)][B(CF)] () of a dpp-Bian radical anion. The reaction of diethylaluminum derivative [(dpp-Bian)AlEt] with 1 equiv of B(CF) gave the cationic complex [{(dpp-Bian)AlEt}F][EtB(CF)] () containing radical-anion dpp-Bian ligands. The paramagnetic compounds , , , , , and were characterized by electron paramagnetic resonance spectroscopy, and the diamagnetic complex was characterized by NMR spectroscopy. The molecular structures of - and were established by single-crystal X-ray diffraction analysis. Compounds and - were found to be active initiators for immortal ring-opening polymerization of ε-caprolactone.