C-H bond activation of ethylene by bare neutral palladium and platinum atoms: a theoretical investigation

The reactions of bare neutral palladium(Pd) and platinum(Pt) atoms with ethylene on both singlet and triplet surfaces were investigated at B3LYP and CCSD (T) levels of theory. The calculated potential energy profiles clearly show that Pt has higher reactivity than Pd toward ethylene. For both Pd and Pt, the reactions on singlet surfaces are energetically more favorable than those on triplet surfaces. However, notable barriers lie on the singlet and triplet surfaces for Pd + ethylene. This result rationalizes the experimental observation that Pd mainly forms p-complex with ethylene. But under high-energy condition, the reaction can proceed to yield dehydrogenation products, Pd-CCH. and Pd (HCCH). For Pt, triplet-singlet surface crossing was suggested to occur in the region where Pt forms p-complex with ethylene to lead the reactions to the energetically more favorable singlet surfaces. For both the two metals, p-complex and C-H bond insertion species are the reaction intermediates and the H.-elimination products are the final products. Copyright (C) 2010 John Wiley & Sons, Ltd.