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Reaction mechanism and Z ‐selectivity for chelated Ru ‐catalyzed AROCM of endic anhydride and propene: A DFT study
Author(s) -
Zhu BaoLin,
Pang XianYong,
Wang GuiChang
Publication year - 2016
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25033
Subject(s) - chemistry , isomerization , propene , olefin fiber , selectivity , catalysis , steric effects , chelation , ring (chemistry) , ligand (biochemistry) , medicinal chemistry , stereochemistry , substituent , density functional theory , electronic effect , computational chemistry , organic chemistry , biochemistry , receptor
Density functional theory calculations were performed to investigate the complete mechanism and selectivity for asymmetric ring opening cross‐metathesis of endic anhydride and propene through a chelated Ru catalyst with nitrato ligand. The preferred mechanism begins with the endic anhydride attacking the catalyst from the “side” position and forming a Ru four‐membered ring complex. Subsequently, the endic anhydride isomerizes with another four‐membered ring complex via the substituent groups rotating their locations. The ring then ruptures and leads to a Ru‐alkylidene complex. Afterward, propene reacts with the Ru‐alkylidene complex through a similar pathway, resulting in rapid a cycloaddition reaction, isomerization to undergo cycloreversion, and the release of (Z)‐ or (E)‐olefin homodimers. The overall preferred mechanism is in accordance with the mechanism of a previously reported chelated Ru catalyst containing a carboxylate ligand. The energy barrier of the transition state for cycloreversion differs by 2.72 kcal/mol from (Z)‐olefin to (E)‐olefin, indicating that the reaction has high Z‐selectivity, in accordance with experimental results. Moreover, cycloreversion is the rate‐determining step. The turnover frequency for selectivity is analyzed to determine the relationship between the theoretically computed catalytic cycle and its experimental counterpart. The activation strain was also analyzed to illustrate the mechanism from the point of quantum chemistry. All of the methods in this article were performed to explain the preference for Z‐olefin, which is attributed to a combination of the steric and electronic effects of the chelated catalyst. Finally, the catalyst is compared with the previously reported chelated Ru catalyst with a carboxylate ligand; results reveal that smaller nitrato sizes lead to higher selectivity efficiency of the catalyst. © 2015 Wiley Periodicals, Inc.