OctaDist, a program for calculating three common octahedral distortion parameters, is presented and the calculation of the trigonal distortion parameter, Θ is standardized for the first time.

Catalysts for aromatic C-O bond activation can potentially be used for the lignin degradation process. We investigated the mechanisms of C-O bond hydrogenolysis of diphenyl ether (PhOPh) by the nickel N-heterocyclic carbene (Ni-SIPr) complex to produce benzene and phenol as products. Our calculations revealed that diphenyl ether is not only a substrate, but also serves as a ligand to stabilize the Ni-SIPr complex. The Ni(SIPr)(η(6)-PhOPh) complex is initially formed before rearranging to Ni(SIPr)(η(2)-PhOPh), the active species for C-O bond activation. The catalytic reaction has three steps: (i) oxidative addition of Ni(SIPr)(η(2)-PhOPh) to form [Ni(SIPr)(OPh)(Ph)](0), (ii) σ-complex-assisted metathesis, in which H2 binds to the nickel to form [Ni(SIPr)(OPh)(Ph)(H2)](0), and then benzene (or phenol) is eliminated, and (iii) reductive elimination of phenol (or benzene) and the binding of PhOPh to regenerate Ni(SIPr)(η(2)-PhOPh). As the rate determining step is the oxidative addition step (+24 kcal mol(-1)), we also calculated the free energy barriers for the oxidative addition of diaryl ether containing a trifluoromethyl electron withdrawing group (PhOC6H4CF3) and found that C-O bond activation at the carbon adjacent to the aryl ring that contains the electron withdrawing substituent is preferred. This is in agreement with the experimental results, in that the major products are phenol and trifluoromethylbenzene. Moreover, the hydrogenation of benzene via Ni(SIPr)(η(2)-C6H6) requires a high energy barrier (+39 kcal mol(-1)); correspondingly, the hydrogenation products, e.g. cyclohexane and cyclohexadiene, were not observed in the experiment. Understanding the reaction mechanisms of the nickel catalysts for C-O bond hydrogenolysis of diphenyl ether will guide the development of catalytic systems for aromatic C-O bond activation to achieve the highest possible selectivity and efficiency.

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The isomerization of 1,5-to 2,6-dimethylnaphthalene (DMN) over β zeolite has been investigated by applying a newly developed density functional named M06-L, incorporated into the ONIOM scheme: M06-L/6-31G(d,p): UFF. Two consecutive reaction mechanisms over the extended zeolite framework have been carefully examined: the 1,5-to 1,6-DMN isomerization followed by the 1,6-to 2,6-DMN isomerization. Both catalytic processes take place via the same mechanism. The isomerization process starts from the protonation of the DMN step, creating the naphthalynic carbocation. Subsequently, the intramolecular methyl shift occurs from the R-position to the adjacent β-position of the naphthalynic carbocation. In the final step, the anionic zeolite framework takes a proton away from the naphthalynic carbocation, yielding a desired 1,6-DMN or 2,6-DMN molecule. The methyl migrations are the rate-determining steps and require activation barriers of 25.69 and 21.05 kcal/ mol for the 1,5-to 1,6-DMN and 1,6-to 2,6-DMN processes, respectively. The calculated reaction profiles are in agreement with the experimental prediction that the 1,5-to 1,6-DMN isomerization is the kinetically controlled step. The results in this study show the excellent performance of a combination of the newly developed functional and the confinement effect represented by the universal force field (M06-L/6-31G(d,p): UFF) for investigating the transformations of aromatic species in the zeolite system.