Reactions of phosphorus/boron frustrated Lewis pairs with SO2

The frustrated Lewis pair tBu3P/B(C6F5)3 (1) readily adds SO2 to yield the zwitterionic adduct tBu3P+–S(O)–OB−(C6F5)3 (3). A series of intramolecular vicinal P/B FLPs Mes2P–(X)–B(C6F5)2 [X = –CH2–CH2– (2a), –CHMe–CH2– (2b), cyclo-C6H10 (5)] add SO2 at −78 °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.