Reactions of phosphorus/boron frustrated Lewis pairs with SO2

The frustrated Lewis pair tBu(3)P/B(C6F5)(3) (1) readily adds SO2 to yield the zwitterionic adduct tBu(3)P(+)-S(O)-OB-(C6F5)(3) (3). A series of intramolecular vicinal P/B FLPs Mes(2)P-(X)-B(C6F5)(2) [X = -CH2-CH2-(2a), -CHMe-CH2- (2b), cyclo-C6H10 (5)] add SO2 at -78 degrees C to yield the corresponding six-membered addition products 4a, 4b, 6. The adducts contain a chiral sulfur center. The [B]-O-(O) S-[P] addition products 3, 4b and 6 were characterized by X-ray diffraction.