Reactions of Indene and Indoles with Platinum Methyl Cations: Indene C−H Activation, Indole π versus Nitrogen Lone-Pair Coordination
journal contributionposted on 15.01.2007 by Travis J. Williams, Jay A. Labinger, John E. Bercaw
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Reactions of indene and various substituted indoles with [(diimine)PtII(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 C2C3 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.