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Olefin Metatheses and Related Reactions Initiated by Carbene Derivatives of Metals in Low Oxidation States
Author(s) -
Katz Thomas J.
Publication year - 2005
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.200462442
Subject(s) - carbene , olefin fiber , tungsten , molybdenum , chemistry , oxidation state , transition metal carbene complex , photochemistry , catalysis , medicinal chemistry , polymer chemistry , organic chemistry
Experiments carried out 24 years ago with tantalum carbenes have led to the much cited hypothesis that metals (other than ruthenium) must be in their highest oxidation states for their carbene derivatives to initiate olefin metatheses. The hypothesis legitimizes the uniqueness of high‐oxidation‐state molybdenum and tungsten carbenes as effective initiators, and it means that the Fischer tungsten carbenes that even earlier were found to initiate olefin metatheses and related transformations must be oxidized before they can be effective. The newer initiators have been termed “well‐defined”, the older “ill‐defined”. But what does the evidence show?