A series of Pt complexes activated by Ag(I) salts have been shown to catalyze Markovnikov hydroarylations of unactivated olefins under mild conditions.

Electrophilic Pt(II) complexes catalyze efficient hydroaminations of olefins by sulfonamides 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 pKa cutoff (conjugate acid pKa < 1) for the participation of nitrogen-containing substrates in this catalysis. Arylsulfonamides (conjugate acid pKa approximately -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 19F and 195Pt 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.

New platinum complexes based on incorporation of the bidentate, monoanionic 2-(2‘-pyridyl)indolide (PyInd) ligand, or two closely related ligands, have been prepared. Reaction of the dimethyl complex K[(PyInd)PtMe2] (K[2a]) in benzene at 150 °C produces the diphenyl species K[(PyInd)PtPh2] (K[3a]), a transformation that appears to proceed via direct oxidative addition of benzene to the 16-electon Pt(II) center. Complex K[2a] also undergoes oxidative addition of Me3SiOTf (OTf = triflate) to give (PyInd)Pt(SiMe3)Me2 (4), a rare five-coordinate Pt(IV)-silyl species. Additionally, reactions that involve stereoselective formation of products of the type (PyInd)Pt(X)(L), including the structurally characterized complexes (PyInd)Pt(Ph)(MeCN) (6) and (PyInd)Pt(Cl)(C2H4) (7), have been observed. These results indicate that the sites trans to the pyridinyl and indolyl fragments of the PyInd ligand are electronically differentiated. Studies of catalytic reactions that presumably proceed via the 14-electron fragment (PyInd)PtR reveal moderate activities for the hydroarylation of norbornene by benzene and other arenes at 140 °C.