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Two-State Reactivity Mechanism of Benzene C–C Activation by Trinuclear Titanium Hydride

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journal contribution
posted on 22.08.2016, 00:00 by Bo Zhu, Wei Guan, Li-Kai Yan, Zhong-Min Su
The cleavage of inert C–C bonds is a central challenge in modern chemistry. Multinuclear transition metal complexes would be a desirable alternative because of the synergetic effect of multiple metal centers. In this work, carbon–carbon bond cleavage and rearrangement of benzene by a trinuclear titanium hydride were investigated using density functional theory. The reaction occurs via a novel “two-state reactivity” mechanism. The important elementary steps consist of hydride transfer, benzene coordination, dehydrogenation, oxidative addition, hydride–proton exchange, and reductive elimination. Most importantly, the ground-state potential energy surface switches from nearly degenerate triplet and antiferromagnetic singlet states to a closed-shell singlet state in the dearomatization of benzene, which effectively decreases the activation barrier. Furthermore, the roles of the transition metal centers and hydrides were clarified.