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Theoretical evidence for bond stretch isomerism in Grubbs olefin metathesis
Author(s) -
Remya Premaja R.,
Suresh Cherumuttathu H.
Publication year - 2017
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.24814
Subject(s) - olefin metathesis , metathesis , chemistry , salt metathesis reaction , associative substitution , catalysis , metallacycle , stereochemistry , polymerization , organic chemistry , physics , x ray crystallography , diffraction , optics , polymer
A comprehensive density functional theory study on the dissociative and associative mechanisms of Grubbs first and second generation olefin metathesis catalysis reveals that ruthenacyclobutane intermediate (RuCB) observed in the Chauvin mechanism is not unique as it can change to a non‐metathetic ruthenacyclobutane (RuCB′) via the phenomenon of bond stretch isomerism (BSI). RuCB and RuCB′ differ mainly in RuC α , RuC β , and C α C β bond lengths of the metallacycle. RuCB is metathesis active due to the agostic type bonding‐assisted simultaneous activation of both C α C β bonds, giving hypercoordinate character to C β whereas an absence of such bonding interactions in RuCB′ leads to typical CC single bond distances and metathesis inactivity. RuCB and RuCB′ are connected by a transition state showing moderate activation barrier. The new mechanistic insights invoking BSI explains the non‐preference of associative mechanism and the requirement of bulky ligands in the Grubbs catalyst design. The present study lifts the status of BSI from a concept of largely theoretical interest to a phenomenon of intense importance to describe an eminent catalytic reaction. © 2017 Wiley Periodicals, Inc.