Metal-alkyl bond protonolysis studies of (dfepe)Pt(Me)X complexes in acidic media

Protonolyses of (dfepe)Pt(Me)X (dfepe = (C2F5)(2)PCH2CH2P(C2F5)(2); X = O2C CF3, OSO2H, OSO2CF3, OSO2F) complexes in their respective neat acid solutio ns cleanly yield (dfepe)Pt(X)(2) products with rates dependent on relative acid strengths. No (dfepe)Pt(Me)(X)(2)(H)(+) intermediates were observed by variable-temperature. NMR in dichloromethane. The (perfluoroaryl)phosphine analogue (dfppe)Pt(Me)(2) (dfppe = (C6F5)(2)PCH2CH2P(C6F5)(2)) is much les s resistant to protonolysis and rapidly converts to (dfppe)Pt(OTf)(2) in HO Tf at 20 degrees C. Kinetic studies for protonolysis in CF3CO2H(D) and CF3S O3H(D) solvents were carried out. Examination of ionic strength and chlorid e anion effects in trifluoroacetic acid indicate that prior association of anion to (dfepe)Pt(Me)X systems is not kinetically important. k(H)/k(D) val ues were obtained from competitive protonolysis studies (CF3CO2H, 9 +/- 2 ( 20 degrees C); H2SO4, 7 +/- 2 (100 degrees C); CF3SO3H, 2.7 +/- 0.7 (100 de grees C)). In the case of CF3CO2H, separate kinetic runs in protio and deut erio acids gave a lower k(H)/k(D) value of 3.6(4). The data obtained in the se studies do not differentiate between limiting S(E)2 and S-E(oxidative) p rotonolysis mechanisms.