The reaction mechanism of the gas-phase Pt atom with C _2H _6 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, PtC _2H _4+H _2 and (H) _2Pt+C _2H _4, the minimal energy reaction pathway involves the rate-determining step of the release of a H _2 or ethene molecule by a reductive elimination mechanism at the exit. For the formation of the side products, PtCH _2+CH _4, the optimal pathway proceeds through the σ-complex cis-HPtC _2H _5 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(CH _3) _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.
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