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Fischer and Schrock carbene complexes in the light of global and local electrophilicity-based descriptors
Journal
Journal of Physical Organic Chemistry
ISSN
08943230
Date Issued
2023-12-01
Author(s)
Patra, Shanti Gopal
Jha, Ruchi
Mondal, Himangshu
Chattaraj, Pratim Kumar
Abstract
The carbon atom (carbene) of Fischer and Schrock complexes are electrophilic and nucleophilic, respectively. The reactivity index electrophilicity is a global reactivity parameter and can tell only about the total electrophilicity of the complexes. To differentiate between the reactivity patterns of these two carbenes, the philicity and multiphilic descriptor are calculated. In Fischer complexes, it is found that the philicity of the nucleophilic attack ((Formula presented.)) is higher than that of philicity of the electrophilic attack ((Formula presented.)) implying the electrophilic nature. A reverse order is found in the Schrock complex pointing nucleophilic character. The multiphilic descriptor (ΔωC = (Formula presented.) − (Formula presented.)) is found to be positive in Fischer but negative in Schrock leading to the same conclusion. Fischer carbene complexes having general formula (CO)5Cr═CH-R (R = CH3, Ph, CCH, CH═CH2, OCH3, OH, NHCH3, and NH2) the order of (Formula presented.) and ΔωC better describe the trend. The trend has been justified through energy decomposition in the purview natural orbital for chemical valence (EDA-NOCV) analysis owing to the π contribution from the R group. The change in the reactivity patterns along the intrinsic reaction coordinate of two representative reactions is plotted. This way of understanding the reactivity parameters would help experimental chemists to predict the catalytic application of carbene complexes of transition metal without the classification of Fischer and Schrock type.
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