Z-Selective Ring-Opening Metathesis Polymerization of 3-Substituted Cyclooctenes by Monoaryloxide Pyrrolide Imido Alkylidene (MAP) Catalysts of Molybdenum and Tungsten
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Author(s)
Jeong, Hyangsoo
Kozera, Daniel J.
Smith, Stacey J.
Zhang, Jihua
Ren, Ning
Hillmyer, Marc A.
Schrock, Richard Royce
Date Issued
August 2013
Journal
Organometallics
Publisher
American Chemical Society (ACS)
Citation
Jeong, Hyangsoo, Daniel J. Kozera, Richard R. Schrock, Stacey J. Smith, Jihua Zhang, Ning Ren, and Marc A. Hillmyer. “Z-Selective Ring-Opening Metathesis Polymerization of 3-Substituted Cyclooctenes by Monoaryloxide Pyrrolide Imido Alkylidene (MAP) Catalysts of Molybdenum and Tungsten.” Organometallics 32, no. 17 (September 9, 2013): 4843–4850.
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Author's final manuscript
Abstract
Ring-opening metathesis polymerization of a series of 3-substituted cyclooctenes (3-MeCOE, 3-HexCOE, and 3-PhCOE) initiated by various Mo and W MAP complexes leads to cis,HT-poly(3-RCOE) polymers. The apparent rate of polymerization of 3-HexCOE by W(N-t-Bu)(CH-t-Bu)(Pyr)(OHMT) (1c; Pyr = pyrrolide; OHMT = O-2,6-Mesityl[subscript 2]C[subscript 6]H[subscript 3]) is greater than the rate of polymerization by Mo(N-t-Bu)(CH-t-Bu)(Pyr)(OHMT) (1b), but both gave the same cis,HT polymer structures. Formation of HT-poly(3-RCOE) employing 1c takes place via propagating species in which the R group (methyl, hexyl, or phenyl) is on C2 of the propagating alkylidene chain, a type of intermediate that has been modeled through the preparation of W(N-t-Bu)(CHCHMeEt)(Pyr)(OHMT). The rate of ROMP is exceedingly sensitive to steric factors: e.g., W(N-t-Bu)(CH-t-Bu)(Me[subscript 2]Pyr)(OHMT), the dimethylpyrrolide analogue of 1c, essentially did not polymerize 3-HexCOE at 22 °C. When a sample of W(N-t-Bu)(CHCHMeEt)(Pyr)(OHMT) and 3-methyl-1-pentene in CDCl[subscript 3] is cooled to −20 °C, the alkylidene resonances for W(N-t-Bu)(CHCHMeEt)(Pyr)(OHMT) disappear and resonances that can be ascribed to protons in a syn[subscript α]/syn[subscript α′] disubstituted trigonal bipyramidal metallacyclobutane complex appear. 3-Methyl-1-pentene is readily lost from this metallacycle on the NMR time scale at room temperature.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/om400583t
