Platinum-based catalysts for the hydroamination of olefins with sulfonamides and weakly basic anilines

Electrophilic Pt(II) complexes catalyze efficient hydroaminations of olefins by sufforiamides and weakly basic anilines. Catalysts include the structurally characterized complex (COD)Pt(OTf)(2) (1) and the known dimer [PtCl2(C2H4)](2), activated by AgBF4. Experiments with substituted anilines establish an empirical pK(a) cutoff (conjugate acid pKa < 1) for the participation of nitrogen-containing substrates in this catalysis, Arylsulfonamides (conjugate acid pK(a). approximate to -6) with various para substituents hydroaminate olefins such as cyclohexene in yields greater than 95% at 90 degrees C. Hydroamination of propylene by p-toluenesulfonamide proceeds with Markovnikov selectivity, suggesting a mechanism that involves olefin activation at Pt. With norbornene and p-toluenesulfonamide as the substrates and 1 as the catalyst, intermediate [(COD)Pt(norbornene)(2)][OTf](2) (3) was identified and characterized by F-19 and Pt-195 NMR spectroscopies and mass spectrometry. Kinetic studies provide the empirical rate law, rate = k(obs)[Pt][sulfonamide], and are consistent with: a mechanism in which attack of a sulfonamide on the Pt-coordinated olefin is the rate-determining step.