Protonolysis of Cationic Pt−C Bonds with Mild Acids:  Can Ligand Torsional Effects Speed Associative Processes?

Tridentate phosphine pincer ligands facilitate the protonolysis of cationic Pt−CH3 compounds (to Pt dications and CH4) with the ammonium acid Ph2NH2·BF4. Large rate enhancements over nonpincer analogues (>50 000) are observed. A mechanism is proposed wherein ring strain present in the planar ground-state arrangement of three phosphine ligands is released in putative five-coordinate intermediates and transition states.