Reactions of phosphorus/boron frustrated Lewis pairs with SO2

Abstract

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.