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]