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Ru‐Oxo catalyzed epoxidations and the woodward–hoffmann rules
Author(s) -
Cundari Thomas R.,
Drago Russell S.
Publication year - 1989
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.560360609
Subject(s) - olefin fiber , chemistry , steric effects , epoxide , catalysis , metal , computational chemistry , stereochemistry , organic chemistry
An analysis of the pathways and intermediates for the epoxidation of olefins using a Ru(IV)‐oxo model complex is presented. Simple bonding concepts, coupled with INDO /1 semiempirical MO calculations, provide a description of the metal‐oxo/olefin interaction that agrees well with experimental facts. Concerted [1 + 2] and [2 + 2] pathways are investigated and found to lead to unfavorable orbital interactions as with organic analogues. Nonconcerted process (those in which one bond is formed before the second), which connect the two concerted pathways, are preferred. A nonconcerted [1 + 2] pathway is preferred over a nonconcerted [2 + 2] pathway on the basis of less steric repulsions between the olefin and the metal ligands. Also, all open structures (those with one CO bond formed) investigated minimized to bound epoxides. In the most favorable pathway, a nonconcerted [1 + 2] pathway, radical cation character on the terminal carbon increases as the nonconcerted process is induced. Preference for the bound epoxide intermediate over the oxometallocycle is simply explained by partial charge considerations.