Reactions of Indene and Indoles with Platinum Methyl Cations: Indene C−H Activation, Indole π versus Nitrogen Lone-Pair Coordination

Reactions of indene and various substituted indoles with [(diimine)Pt^(II)(Me)(TFE)]^+ cations have been studied (diimine = ArNC(Me)−C(Me)NAr; TFE = 2,2,2-trifluoroethanol). Indene displaces the TFE ligand from platinum to form a stable π coordination complex that, upon heating, undergoes C−H activation with first-order kinetics, ΔH^⧧ = 29 kcal/mol, ΔS^⧧ = 10 eu, and a kinetic isotope effect of 1.1 at 60 °C. Indoles also initially form coordination complexes through the C_2=C_3 olefin, but these undergo rearrangement to the corresponding N-bound complexes. The relative rates of initial coordination and rearrangement are affected by excess acid or methyl substitution on indole.