Investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.
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| Format: | Thesis |
| Language: | eng |
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Massachusetts Institute of Technology
2014
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| Online Access: | http://hdl.handle.net/1721.1/84373 |
| _version_ | 1811089650692915200 |
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| author | Gerber, Laura Claire Heidkamp |
| author2 | Richard R. Schrock. |
| author_facet | Richard R. Schrock. Gerber, Laura Claire Heidkamp |
| author_sort | Gerber, Laura Claire Heidkamp |
| collection | MIT |
| description | Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013. |
| first_indexed | 2024-09-23T14:22:34Z |
| format | Thesis |
| id | mit-1721.1/84373 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T14:22:34Z |
| publishDate | 2014 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/843732019-04-11T10:52:33Z Investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis Gerber, Laura Claire Heidkamp Richard R. Schrock. Massachusetts Institute of Technology. Department of Chemistry. Massachusetts Institute of Technology. Department of Chemistry. Chemistry. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013. Cataloged from PDF version of thesis. Vita. Includes bibliographical references. Chapter 2 investigates the mechanism of the temperature-controlled polymerization of 3- methyl-3-phenylcyclopropene (MPCP) by Mo(NAr)(CHCMe 2Ph)(Pyr)(OTPP) (Ar = 2,6- diisopropylphenyl, Pyr = pyrrolide, OTPP = 2,3,5,6-tetraphenylphenoxide). Cissyndiotactic poly(MPCP) is obtained at -78 °C, while atactic poly(MPCP) is obtained at ambient temperature. The syn initiator (syn refers to the isomer in which the substituent on the alkylidene points towards the imido ligand and anti where the substituent points away) reacts with MPCP to form an anti first-insertion product at low temperatures, which continues to propagate to give cis,syndiotactic polymer. At higher temperatures, the anti alkylidenes that form initially upon reaction with MPCP rotate thermally to syn alkylidenes on a similar timescale as polymer propagation, giving rise to an irregular polymer structure. In this system cis,syndiotactic polymer is obtained through propagation of anti alkylidene species. Chapters 3 - 5 detail the synthesis and reactivity of compounds containing a 2,6- dimesitylphenylimido (NAr*) ligand in order to provide a better understanding of the role of steric hindrance in olefin metathesis catalysts. A new synthetic route to imido alkylidene complexes of Mo and W, which proceeds through mixed-imido compounds containing both NAr* and NtBu ligands, was developed to incorporate the NAr* ligand. Alkylidene formation is accomplished by the addition of 3 equivalents of pyridine*HCl to Mo(NAr*)(NBu)(CH 2CMe2Ph)2 or the addition of 1 equivalent of pyridine followed by 3 equivalents of HCl solution to W(NAr*)(N'Bu)(CH 2CMe2Ph)2 to provide M(NAr*)(CHCMe 2Ph)Cl 2(py) (py = pyridine). Monoalkoxide monochloride, bispyrrolide, and monoalkoxide monopyrrolide (MAP) compounds are isolated upon substitution of the chloride ligands. Reaction of W MAP complexes (W(NAr*)(CHCMe 2Ph)(Me2Pyr)(OR)) with ethylene allows for the isolation of unsubstituted metallacycle complexes W(N Ar*)(C 3H6)(Me 2Pyr)(OR) (R = CMe(CF 3)2, 2,6-Me2C6H3, and SiPh 3). By application of vacuum to solutions of unsubstituted metallacyclebutane species, methylidene complexes W(NAr*)(CH 2)(Me2Pyr)(OR) (R = tBu, 2,6-Me2C6H3, and SiPh 3) are isolated. Addition of one equivalent of 2,3- dicarbomethoxynorbornadiene to methylidene species allows for the observation of firstinsertion products by NMR spectroscopy. Investigations of NAr* MAP compounds as catalysts for olefin metathesis reactions show that they are active catalysts, but not E or Z selective for ring-opening metathesis polymerization the homocoupling of 1-octene or 1,3-dienes. Methylidene species W(NAr*)(CH 2)(Me2Pyr)(OR) (R = 2,6-Me 2C6H3 or SiPh3) catalyze the ring-opening metathesis or substituted norbornenes and norbornadienes with ethylene. by Laura Claire Heidkamp Gerber. Ph.D. 2014-01-23T18:39:43Z 2014-01-23T18:39:43Z 2013 2013 Thesis http://hdl.handle.net/1721.1/84373 867635229 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 217 pages application/pdf Massachusetts Institute of Technology |
| spellingShingle | Chemistry. Gerber, Laura Claire Heidkamp Investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis |
| title | Investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis |
| title_full | Investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis |
| title_fullStr | Investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis |
| title_full_unstemmed | Investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis |
| title_short | Investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis |
| title_sort | investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis |
| topic | Chemistry. |
| url | http://hdl.handle.net/1721.1/84373 |
| work_keys_str_mv | AT gerberlauraclaireheidkamp investigationsofstericallydemandingligandsinmolybdenumandtungstenmonopyrrolidemonoalkoxidecatalystsforolefinmetathesis |