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Remarkable Ability of the Benzylidene Ligand To Control Initiation of Hoveyda–Grubbs Metathesis Catalysts
Author(s) -
Basak Tymoteusz,
Grudzień Krzysztof,
Barbasiewicz Michał
Publication year - 2016
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201600435
Subject(s) - chemistry , steric effects , ligand (biochemistry) , metathesis , ruthenium , catalysis , chelation , enyne metathesis , ring (chemistry) , combinatorial chemistry , salt metathesis reaction , stereochemistry , catalytic cycle , ring opening metathesis polymerisation , associative substitution , naphthalene , organic chemistry , biochemistry , receptor , polymerization , polymer
The structure of the chelating benzylidene ligand offers the unique ability to control the initiation of Hoveyda–Grubbs metathesis catalysts. Apart from steric and electronic effects acting on the step involving opening of the chelate ring, changes related to the following ligand‐exchange process may also play a critical role. Our mechanistic model reveals that ligands substituted at the 6‐position of the benzylidene ring enter the metathesis cycle in a nonoptimal chelating conformation, and thus the coordination number of the ruthenium center transiently increases to six (associative mechanism). In effect, the synthesis and initiation of the catalysts becomes difficult, and the energy barrier of the ligand‐exchange process is controlled by the structure of the coordinating OR group. Moreover, we explain how isomeric naphthalene ligands affect the catalytic performance by an indivisible combination of steric and π‐electron delocalization effects.