Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes
We have synthesized and characterized tungsten oxo alkylidene biphenolate complexes with the formulas W(O)(CHR)(rac-biphenolate)(PPhMe2) and (R,S)-[W(μ-O)(CHR)(biphenolate)]2 (R = CMe2Ph; biphenolate = L1 or L2 in the text). They behave as initiators for the stereoselective (cis,isotactic) polymeriz...
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American Chemical Society (ACS)
2020
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| Online Access: | https://hdl.handle.net/1721.1/124980 |
| _version_ | 1826195162835976192 |
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| author | Yan, Tao VenkatRamani, Sudarsan Schrock, Richard R. Müller, Peter |
| author2 | Massachusetts Institute of Technology. Department of Chemistry |
| author_facet | Massachusetts Institute of Technology. Department of Chemistry Yan, Tao VenkatRamani, Sudarsan Schrock, Richard R. Müller, Peter |
| author_sort | Yan, Tao |
| collection | MIT |
| description | We have synthesized and characterized tungsten oxo alkylidene biphenolate complexes with the formulas W(O)(CHR)(rac-biphenolate)(PPhMe2) and (R,S)-[W(μ-O)(CHR)(biphenolate)]2 (R = CMe2Ph; biphenolate = L1 or L2 in the text). They behave as initiators for the stereoselective (cis,isotactic) polymerization of 2,3-dicarbomethoxy-5-norbornadiene and eight enantiomerically pure 5-substituted norbornenes with a cis,isotactic precision of 95–98% in most cases. The active initiators are 14e W(O)(CHR)(biphenolate) complexes, which are formed through either dissociation of PPhMe2 from the phosphine adducts or scission of the heterochiral dimer. Addition of B(C6F5)3 (one per W) to (R,S)-[W(μ-O)(CHR)(L1)]2 led to formation of what we propose to be monomeric W[OB(C6F5)3](CHR)(L1) in equilibrium with B(C6F5)3 and (R,S)-[W(μ-O)(CHR)(L1)]2. This mixture decomposed over a period of 1–2 h, was much slower to initiate polymerization than (R,S)-[W(μ-O)(CHR)(L1)]2, and was much less stereoselective. Polymerization of five of the monomers with the imido alkyidene initiator, W(N-2,6-Me2C6H3)(CHCMe2Ph)(rac-L1), gave virtually identical results compared to the results obtained with oxo complexes. |
| first_indexed | 2024-09-23T10:08:09Z |
| format | Article |
| id | mit-1721.1/124980 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T10:08:09Z |
| publishDate | 2020 |
| publisher | American Chemical Society (ACS) |
| record_format | dspace |
| spelling | mit-1721.1/1249802022-09-26T15:57:39Z Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes Yan, Tao VenkatRamani, Sudarsan Schrock, Richard R. Müller, Peter Massachusetts Institute of Technology. Department of Chemistry We have synthesized and characterized tungsten oxo alkylidene biphenolate complexes with the formulas W(O)(CHR)(rac-biphenolate)(PPhMe2) and (R,S)-[W(μ-O)(CHR)(biphenolate)]2 (R = CMe2Ph; biphenolate = L1 or L2 in the text). They behave as initiators for the stereoselective (cis,isotactic) polymerization of 2,3-dicarbomethoxy-5-norbornadiene and eight enantiomerically pure 5-substituted norbornenes with a cis,isotactic precision of 95–98% in most cases. The active initiators are 14e W(O)(CHR)(biphenolate) complexes, which are formed through either dissociation of PPhMe2 from the phosphine adducts or scission of the heterochiral dimer. Addition of B(C6F5)3 (one per W) to (R,S)-[W(μ-O)(CHR)(L1)]2 led to formation of what we propose to be monomeric W[OB(C6F5)3](CHR)(L1) in equilibrium with B(C6F5)3 and (R,S)-[W(μ-O)(CHR)(L1)]2. This mixture decomposed over a period of 1–2 h, was much slower to initiate polymerization than (R,S)-[W(μ-O)(CHR)(L1)]2, and was much less stereoselective. Polymerization of five of the monomers with the imido alkyidene initiator, W(N-2,6-Me2C6H3)(CHCMe2Ph)(rac-L1), gave virtually identical results compared to the results obtained with oxo complexes. National Science Foundation (CHE-1463707) 2020-05-01T18:57:17Z 2020-05-01T18:57:17Z 2019-08 2019-06 Article http://purl.org/eprint/type/JournalArticle 0276-7333 1520-6041 https://hdl.handle.net/1721.1/124980 Yan, Tao et al. "Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes." Organometallics 38, 16 (August 2019): 3144-3150 © 2019 American Chemical Society http://dx.doi.org/10.1021/acs.organomet.9b00377 Organometallics Creative Commons Attribution-NonCommercial-NoDerivs License http://creativecommons.org/licenses/by-nc-nd/4.0/ application/pdf American Chemical Society (ACS) ACS |
| spellingShingle | Yan, Tao VenkatRamani, Sudarsan Schrock, Richard R. Müller, Peter Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes |
| title | Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes |
| title_full | Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes |
| title_fullStr | Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes |
| title_full_unstemmed | Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes |
| title_short | Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes |
| title_sort | synthesis of tungsten oxo alkylidene biphenolate complexes and ring opening metathesis polymerization of norbornenes and norbornadienes |
| url | https://hdl.handle.net/1721.1/124980 |
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