Aluminabenzene-Rh and -Ir Complexes: Synthesis, Structure, and Application toward Catalytic C-H Borylation.

Aluminabenzene-rhodium and -iridium complexes were synthesized, in which the aluminum atom played as a proximal Lewis acidic site. Based on their structural analysis, aluminabenzene ligand could coordinate to Rh and Ir as a η5-pentadienyl ligand. The Lewis acidic character of aluminum atom in aluminabenzene ligand was confirmed by treatment with 4-dimethylaminopyridine to form the corresponding Lewis acid-base complexes. In addition, the α-selective C-H borylation of triethylamine with the aluminabenzene-ligated iridium catalyst was demonstrated.