Promoting C-C Bond Coupling of Benzyne and Methyl Ligands in Electron-Deficient (triphos)Pt-CH₃⁺ Complexes

In situ generated benzyne reacts at room temperature with (triphos)Pt-CH₃⁺ to form a five-coordinate π-complex (2) that is isolable and stable in solution. Thermolysis of 2 at 60 °C generates (triphos)Pt(o-tolyl)⁺ (3), which is the product of formal migratory insertion of CH₃^- onto the coordinated benzyne. The reaction of 2 with the acid Ph₂NH₂⁺ yields toluene at room temperature over the course of 8 h, while the same reaction with 3 only proceeds to 40% conversion over 2 days. These data indicate that the protonolysis of 2 does not proceed by CH₃ migration onto benzyne to form 3 followed by protodemetalation. Instead, the data suggest either that protonation of 2 is first and is followed by H migration to yield a Pt^IVPh(Me) dication or that this latter species is generated by direct protonolysis of coordinated benzyne prior to reductive elimination of toluene.