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 = O2CCF3, OSO2H, OSO2CF3, OSO2F) complexes in their respective neat acid solutions 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 less resistant to protonolysis and rapidly converts to (dfppe)Pt(OTf)(2) in HOTf at 20 degrees C. Kinetic studies for protonolysis in CF3CO2H(D) and CF3SO3H(D) solvents were carried out. Examination of ionic strength and chloride 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) values were obtained from competitive protonolysis studies (CF3CO2H, 9 +/- 2 (20 degrees C); H2SO4, 7 +/- 2 (100 degrees C); CF3SO3H, 2.7 +/- 0.7 (100 degrees C)). In the case of CF3CO2H, separate kinetic runs in protio and deuterio acids gave a lower k(H)/k(D) value of 3.6(4). The data obtained in these studies do not differentiate between limiting S(E)2 and S-E(oxidative) protonolysis mechanisms.