Activation of C–H and C–C bonds of ethane by gas-phase Pt atom: Potential energy surface and reaction mechanism.

Abstract: The reaction mechanism of the gas-phase Pt atom with C₂H₆ has been systematically studied on the singlet and triplet potential energy surfaces at CCSD(T)//BPW91/6-311++G(d, p), Lanl2dz level. For the formation of the main products, PtC₂H₄ +H₂ and (H)₂Pt+C₂H₄, the minimal energy reaction pathway involves the rate-determining step of the release of a H₂ or ethene molecule by a reductive elimination mechanism at the exit. For the formation of the side products, PtCH₂ +CH₄, the optimal pathway proceeds through the σ-complex cis-HPtC₂H₅ from initial C–H bond cleavage, which assists the C–C σ-bond metathesis. This reactivity mode is complementary for the classical reactivity picture through the C–C cleavage intermediate M(CH₃)₂. Besides, these results are in qualitative agreement with the experimental results, in which the C–H insertion product is experimentally observed and the C–C insertion product is not formed in observable quantity. [Copyright &y& Elsevier]