Formation of Alternating trans-A-alt-B Copolymers through Ring-Opening Metathesis Polymerization Initiated by Molybdenum Imido Alkylidene Complexes
Name
Schrock_Formation of with SI.pdf
Size
3.25 MB
Format
Adobe PDF
Checksum (MD5)
e5df9ae18ea25d87139eef001a4fa600
Author(s)
Jeong, Hyangsoo
John, Jeremy M
Schrock, Richard Royce
Date Issued
October 2015
Journal
Organometallics
Publisher
American Chemical Society (ACS)
Citation
Jeong, Hyangsoo, Jeremy M. John, and Richard R. Schrock. “Formation of Alternating trans-A-alt-B Copolymers through Ring-Opening Metathesis Polymerization Initiated by Molybdenum Imido Alkylidene Complexes.” Organometallics 34.20 (2015): 5136–5145.
Version
Author's final manuscript
Abstract
Ring-opening metathesis polymerization (ROMP) is used to prepare trans-poly(A-alt-B) polymers from a 1:1 mixture of A and B where A is a cyclic olefin such as cyclooctene (A[subscript 1]) or cycloheptene (A[subscript 2]) and B is a large norbornadiene or norbornene derivative such as 2,3-dicarbomethoxy-7-isopropylidenenorbornadiene (B[subscript 1]) or dimethylspirobicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate-7,1'cyclopropane (B[subscript 2]). The most successful initiators that were
examined are of the type Mo(NR)(CHCMe[subscript 2]Ph)[OCMe(CF[subscript 3])[subscript 2]][subscript 2] (R = 2,6-Me[subscript 2]C[subscript 6]H[subscript 3] (1) or 2,6-iPr[subscript 2]C[subscript 6]H[subscript 3] (2)). The trans configuration of the AB linkages is proposed to result from the steric demand of B. Both anti-MB and syn-MB alkylidenes are observed during the copolymerization, where B was last inserted into a Mo=C bond, although anti-MB dominates as the reaction
proceeds. Anti-MB is lower in energy than syn-MB, does not react readily with either A or B, and interconverts slowly with syn-MB through rotation about the Mo=C bond. Syn-MB does not readily react with B, but it does react slowly with A (rate constant ~1 M[superscript -1] s
[superscript -1]) to give anti-MA and one trans-AB linkage. Anti-MA then reacts with B (rate constant ~300 M[superscript -1] s[superscript -1] or larger) to give syn-MB and the second trans-AB linkage. The reaction has been modeled using experimental data in order to obtain the estimated rate constants above. The reaction between anti-MA and A is proposed to give rise to AA linkages, but AA dyads can amount to <5%. Several other possible A and B monomers, initiators, and conditions were explored.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1021/acs.organomet.5b00709
