Stoichiometric and Catalytic Arene Activations by Platinum Complexes Containing Bidentate Monoanionic Nitrogen-Based Ligands

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.