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Journal of the American Chemical Society
pied neighboring BAS is present. A dramatically low ꢀGǂ
(62 kJ·mol-1) was obtained and the concerted C−C and
W−C bond scissions are more exothermic (ꢀG = -103
kJ·mol-1). The cooperation between the active W=CHCH3
and the unoccupied neighboring BAS is shown to play a
key role in increasing olefin metathesis reaction rate, de-
spite that the experimental Ea for WOx/USY (29.9 kJ·mol-1,
Fig. 1F) cannot allow a direct comparison with the activa-
tion barrier obtained from DFT calculation. The value of
experimental Ea is indicative of diffusion limitation which
leads to a complex rate-temperature relationship.41 Upon
releasing the first propene, a reactive W=CH2 is formed
and is ready for the adsorption of trans-2-butene to form
a W cyclobutane intermediate subsequently. It is found
that the adsorption of trans-2-butene and the formation
of the W cyclobutane intermediate are affected by the
presence of the unoccupied neighboring BAS. More im-
portantly, the calculated ꢀGǂ of the second concerted C−C
and W−C bond scissions in the presence of the unoccu-
pied neighboring BAS (53 kJ·mol-1) is much lower than
that without BAS present (86 kJ·mol-1).
tion, and suggested future work supplied as Supporting In-
formation. This material is available free of charge via the
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AUTHOR INFORMATION
Corresponding Author
* edman.tsang@chem.ox.ac.uk
Author Contributions
† contributed equally as co-first author.
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Present Addresses
‡ College of Chemical Engineering, Beijing University of
Chemical Technology, China.
ACKNOWLEDGMENT
The STEM, EXAFS and SXRD facilities provided by Diamond
Light Source (UK) are acknowledged.
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4. CONCLUSIONS
We have designed a new type of bifunctional olefin
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ASSOCIATED CONTENT
Supporting Information. Methods and additional results of
catalyst testing, structure refinement, physical characteriza-
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