Theoretical Interpretation of the Cyclohexane -> Benzene Reaction on the Pt(111) Surface

Article abstract of DOI:10.1021/ja00312a009

Cyclohexane is found to bind most strongly to Pt(111) when three axial CH bonds are directly over three surface metal atoms.Bonding to the surface is caused by CH ? donation to the surface which also serves to weaken the CH bonds as noted in the experimental literature.The hydrogen atoms in the axial bonds are easily transferred to surface platinum atoms, with decreasing activation barriers as the C6Hn intermediate settles closer to the surface as a result of metal-carbon bonding.The barriers to equatorial CH bond scission from C6H9 are lower still.The strong CH activation is a consequence of a CH ? donation bond to the surface.Before the transition state is reached during the stretch of a CH bond, the antibonding counterpart orbital to this 3-center C-H-Pt bond donates its electrons, to the conduction band.Consequently, the C-H-Pt bond order in the transition state is one.These results explain the experimental observation of benzene formation at low temperature.