B. de Bruin
- Exchange of organic radicals with organo-cobalt complexes formed in the living radical polymerization of vinyl acetate
- Journal of the American Chemical Society
- Volume | Issue number
- 130 | 40
- Pages (from-to)
- Document type
- Faculty of Science (FNWI)
- Van 't Hoff Institute for Molecular Sciences (HIMS)
Exchange of organic radicals between solution and organo-cobalt complexes is experimentally observed and the reaction pathway is probed through DFT calculations. Cyanoisopropyl radicals from AIBN (2,2'-azobisisobutyronitrile) enter solutions of cobalt(II) tetramesityl porphyrin ((TMP)Co-II center dot, 1) and vinyl acetate (VAc) in benzene and react to produce transient hydride (TMP)Co-H and radicals (center dot CH(OAc)CH2C(CH3)(2)CN (R-1 center dot)) that proceed on to form organo-cobalt complexes (TMP)Co-CH(OAc)CH3 (4, Co-R-2) and (TMP)Co-CH(OAc)CH2C(CH3)(2)CN (3, Co-R-1), respectively. Rate constants for cyanoisopropyl radical addition with vinyl acetate and hydrogen atom transfer to (TMP)Co-II center dot are reported through kinetic studies for the formation and transformation of organo-cobalt species in this system. Rate constants for near-degenerate exchanges of radicals in solution with organo-cobalt complexes are deduced from H-1 NMR studies and kinetic modeling. DFT computations revealed formation of an unsymmetrical adduct of (TMP)Co-CH(OAc)CH3 (4) with center dot CH(OAc)CH3 (R-2 center dot) and support an associative pathway for radical interchange through a three-centered three-electron transition state [R center dot center dot center dot Co center dot center dot center dot R]. Associative radical interchange of the latent radical groups in organo-cobalt porphyrin complexes with freely, diffusing radicals in solution that is observed in this system provides a pathway for mediation of living radical polymerization of vinyl acetate.
- go to publisher's site
If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library, or send a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.