Flash Communication: Properties and Applications of a Pentavalent Bromoantimony Lewis Acid

While normally reluctant toward oxidation, SbBr3 can be oxidized with 3,4,5,6-tetrachloro-1,2-benzoquinone (o-chloranil) in the presence of a Lewis base like the bromide anion or triphenylphosphine oxide (PPh3O) to form the tetrachlorocatecholate (catCl) derivatives [SbBr4(catCl)]− ([2-Br]−) and SbBr3(catCl)•OPPh3 (2•OPPh3), respectively. Structural, spectroscopic, and computational data indicate that the SbBr3(catCl) fragment is similarly, if slightly less, Lewis acidic than the previously reported SbCl3(catCl) fragment. The SbBr3/o-chloranil system, as well as its previously reported counterpart SbCl3/o-chloranil, were tested as Lewis acid catalysts for C–O bond metathesis and polycarbonate depolymerization. These results identified SbX3/o-chloranil pairs (X = Cl, Br) as simple main-group platforms for C–O bond cleavage chemistry.