Understanding Metal-Free Catalytic Hydrogenation: A Systematic Theoretical Study of the Hydrogenation of Ethene

Metal-free catalytic hydrogenation of ethene has been examined using high-level [G3(MP2)-RAD] ab initio molecular orbital theory. The dependence of the catalytic activity on the nature of the catalyst Z–X–H has been explored. We find that the catalytic activity is generally greater as Z–X–H becomes more acidic, both for first- and second-row atoms X. Molecules in which X is a second-row atom generally lead to more effective catalysis than the corresponding first-row analogues. The proton affinity at X of Z–X–H also contributes significantly to the catalysis in some cases (e.g. amines).