Complementary anion binding by bidentate boron-containing Lewis acids

Article abstract of DOI:10.1016/j.jorganchem.2005.01.015

Anion binding by the pyroborates (catB)₂O (1, cat = O ₂C₆H₄-1,2) and (S,S-Ph₂C ₂H₂O₂B)₂O (2) has been investigated by spectroscopic, structural and titration methods. 1 has been shown to act as a bifunctional Lewis acid, exemplified by the complementary (1:1) binding of bidentate bases such as acetate and dihydrogen phosphate. The former complex has been characterized in the solid state by X-ray diffraction and a binding constant of 1500 ± 550 M^-1 determined in chloroform solution. The reaction of 2 with acetate, by contrast, leads to breakdown of the Lewis acid chelate and to the formation of the homochiral borate anion [(S,S-Ph ₂C₂H₂O₂)₂B]^- in good yield (84% based on the chiral component).