Insertion reactions of SO2 into Pd–OR bonds: preparation of alkyl sulfito complexes of palladium(ii)

Abstract

Mononuclear palladium–hydroxo complexes of the type [Pd(N–N)(C₆F₅)(OH)] [(N–N = 2,2′-bipyridine (bipy), 4,4′-dimethyl-2,2′-bipyridine (Me₂bipy), or N,N,N′,N′-tetramethylethylenediamine (tmeda) react with SO₂ (1 atm) at room temperature in alcohol (methanol, ethanol, propanol or isopropanol) to yield alkyl sulfito palladium complexes [Pd(N–N)(C₆F₅)(SO₂OR)] (R = Me, Et, Pr or ⁱPr). Similar alkyl sulfito complexes [Pd(N–N)(C₆F₅)(SO₂OR)] (N–N = bis(3,5-dimethylpyrazol-1-yl)methane); R = Me or Et) are obtained when [Pd(N–N)(C₆F₅)Cl] is treated with KOH in the corresponding alcohol ROH and SO₂ is bubbled through the solution. The reaction of [Pd(bipy)(C₆F₅)(OH)] with SO₂ in tetrahydrofuran gives [Pd(N–N)(C₆F₅)(SO₂OH)]. The X-ray diffraction study of [Pd(tmeda)(C₆F₅)(SO₂OPr)] has established the sulfur coordination of the propyl sulfito ligand.