Z-Selective Ring-Opening Metathesis Polymerization of 3-Substituted Cyclooctenes by Monoaryloxide Pyrrolide Imido Alkylidene (MAP) Catalysts of Molybdenum and Tungsten
Author(s)Jeong, Hyangsoo; Kozera, Daniel J.; Smith, Stacey J.; Zhang, Jihua; Ren, Ning; Hillmyer, Marc A.; Schrock, Richard Royce; ... Show more Show less
MetadataShow full item record
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.
DepartmentMassachusetts Institute of Technology. Department of Chemistry
American Chemical Society (ACS)
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.
Author's final manuscript