Catalytic Reactions Involving Activation of O-H Bonds

Catalytic Reactions Involving Activation of O-H Bonds 205 1 mol% AgOTf... 

This reaction is considered as a model of the catalytic reaction. In this work, CpM(CO)2[B(OR)2] (M=Fe, Ru,or W) was employed as a catalyst. Interestingly, the reaction proceeds through the oxidative addition and the reductive elimination for both methane and benzene in the W complex, where the W(V) complex is involved as an intermediate. On the other hand, the Fe-catalyzed reaction proceeds in one step for both methane and benzene, where the Fe(V) species is not involved as an intermediate but the Fe center takes +V oxidation state in the transition state. Thus, the reaction is considered to be metathesis. In the Ru complex, the reaction proceeds through the Ru(V) intermediate for the C-H o-bond activation of benzene, while it proceeds in one step for the C-H o-bond activation of methane hke that of the Fe complex. The differences among three metals can be interpreted in terms of the d orbital energy and/or the d" d" s promotion energy, as discussed above. 

As far as activation of the C-H bond in aromatic compounds with palladium(ll) is concerned, the features of these catalytic reactions are the following (1) hydrogen atom is departed at the first step as a proton (2) electrons of the activated C-H bond are involved in the formation of organopalladium intermediate (3) palladium(ll) is reduced into palladium (O), which then undergoes oxidation with an external oxidant into palladium(ll) acetate, thus providing a cyclic catalytic process (Scheme 4). 

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