Help Privacy Policy Disclaimer
  Advanced SearchBrowse




Journal Article

Model Studies of Methacrylate Chain Transfer Polymerization Mediated by Cationic Zirconocene tert-Butyl Enolate


Lehmann,  Christian W.
Service Department Lehmann (EMR), Max-Planck-Institut für Kohlenforschung, Max Planck Society;

External Resource
No external resources are shared
Fulltext (restricted access)
There are currently no full texts shared for your IP range.
Fulltext (public)
There are no public fulltexts stored in PuRe
Supplementary Material (public)
There is no public supplementary material available

Lian, B., Lehmann, C. W., Navarro, C., & Carpentier, J.-F. (2005). Model Studies of Methacrylate Chain Transfer Polymerization Mediated by Cationic Zirconocene tert-Butyl Enolate. Organometallics, 24(10), 2466-2472. doi:10.1021/om050119m.

Cite as: https://hdl.handle.net/11858/00-001M-0000-000F-9551-5
Enolizable ketones and thiols have been investigated as potential transfer agents for methyl methacrylate (MMA) polymerization mediated by the Cp2ZrMe2/B(C6F5)3 system. Addition of 1−10 equiv of acetophenone, acetone, or thiophenols inhibits polymerization, while the system tolerates the presence of tert-butylthiol (tBuSH). In this case, a moderate decrease in the molecular weight of the PMMAs is observed. The stoichiometric reactivity of these organic acids toward the cationic ester enolate complex [Cp2Zr(THF)(O(tBuO)C=CMe2)]+[MeB(C6F5)3]- (1), which models the active species for MMA polymerization, has been investigated. Ketones undergo aldolization reactions with 1 to generate species that are inactive in MMA polymerization. Thiols readily cleave the Zr−O bond of 1 to give [Cp2Zr(SR)(THF)]+ cations (R = tBu, 4; SC6H4-p-Cl, 6; SC6H4-o-OMe, 7). The crystal structure of 7 has been determined. In the presence of a tert-butyl ester R‘CO2tBu, thiolato complexes 4, 6, and 7 smoothly decompose into the corresponding cationic carboxylato complex [Cp2Zr(THF)(O2CR‘)]+ (R‘ = iPr, 5; CH3, 9) and thiol RSH, with release of isobutene. tert-Butylthiolato complex 4 and the in situ combination Cp2Zr(StBu)Me/B(C6F5)3 polymerized quantitatively MMA in toluene to yield PMMAs with narrow dispersity (Mn/Mw = 1.26−1.48), but with molecular weight much higher than the expected Mn values, consistent with poor initiation efficiency and/or instability.