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Indexed by:期刊论文

Date of Publication:2014-03-10

Journal:ORGANOMETALLICS

Included Journals:SCIE、Scopus

Volume:33

Issue:5

Page Number:1126-1134

ISSN No.:0276-7333

Abstract:DFT studies have been performed for the process of methane elimination via an intramolecular C-H bond activation of the polymethyl trinuclear rare-earth-metal complex [(eta(5)-C5Me4SiMe3)Tm(mu(2)-CH3)(2)](3). It has been found that intermetallic cooperation plays an important role in achieving such an intramolecular C-H bond activation process, and the cooperation of trimetallic centers makes the C-H bond activation kinetically easier in comparison with that of bimetallic centers. The methane elimination reaction occurs through rearrangement of Tm-CH3 connections and subsequent C-H bond activation. The C-H bond activation is the rate-determining step of the whole process, and the corresponding transition state is characterized by a sigma-bond metathesis assisted by cooperation of multimetal sites. Such a C-H bond activation step was accomplished by a change in the coordination manner (from mu(2) to mu(3) fashion) of a methyl group and a subsequent hydrogen transfer, and the two events are asynchronous concerted processes. The computational results also suggest that the reactivity of the CH bond of the metal-connected CH3 group follows the order mu(3)-C(H-2)-H > mu(2)-C(H-2)H > mu(1)-C(H-2)-H. This is unlike the case of a metal-CH3 bond, where the terminal methyl (monometal-connected mu(1)-CH3) is generally more reactive than multimetal-connected methyls. In addition, the effect of 4f electrons of such trinuclear organolanthanide compounds on the geometry and energy profile studied here is also discussed.