Abstract
The reaction paths for the conversion of chlorobenzene to p-chlorophenol are presented in detail using iron and manganese monoxides via the hydroxo insertion intermediate, HO–M–C6H4Cl (M=FeO, MnO). The molecular geometries and electronic structures for the reactants, intermediates, transition states, and products were optimized and analyzed in detail by density functional methods. The reaction potential surface profiles indicate that the metaloxo species can activate the para C–H bond of the chlorobenzene to lead to the p-chlorophenol via the successive formation and the dissociation of the metal carbon bond, followed by removal of the metal atom (Fe or Mn). The intrinsic reaction co-ordinate (IRC) analyses indicated that no crossover point was searched for between the high-spin and low-spin potential energy surfaces; thus, no spin crossing was found between these two states potential energy surfaces. The low-spin potential energy surface lies above the high-spin one for the entire reaction pathway. Our theoretical study on the possible reaction pathways for the conversion of chlorobenzene to p-chlorophenol will also be useful for analyzing the catalytic functions of C–H bond activation and metal–carbon bond formation by transition metal complexes.
Highlights
Transition metals and their oxides are widely used as both catalysts and catalytic supports for C–H bond activation [1,2,3,4,5]
Andrew’s group has reacted some of the group IV transition metal atoms with acetonitrile; the observed experimental product CH2=Zr(H)NC was assigned by matrix isolation infrared spectroscopy and isotopic substituted experiments combing with DFT frequency analysis, the detailed reaction mechanism was not took into account [16]
We conclude that the chlorobenzene–p-chlorophenol reaction is a two-step reaction: in the first step, the compound passes through a transition state (TS1) to form a hydroxyl intermediate (HOM-C6H4Cl); in the second step, another transition state (TS2) forms that leads to the product
Summary
Transition metals and their oxides are widely used as both catalysts and catalytic supports for C–H bond activation [1,2,3,4,5]. These materials have not yet been fully investigated from a comprehensive mechanistic viewpoint [6]. Besides the reactions of pure transition metal compounds with methane and acetonitrile, some small hydrocarbons such as C2H2, C2H4, and C6H6 [18,19,20] and halohydrocarbons such as CH3Cl [21,22,23,24] have been reported. The reactions of pure transition metal oxides with halogenated aromatic hydrocarbons have received very little attention
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