Cyclopropene polymerization and enyne metathesis catalyzed by high oxidation state molybdenum alkylidenes

Chapter 1. An olefin metathesis reaction between Mo(NAr)(CHCMe2Ph)(OCMe(CF3)2)2 (Ar = 2,6diisopropylphenyl) and trans-i 1,4-divinylbenzene or trans, trans- 1,4-di-buta- 1,3-dienylbenzene (5) results in the formation of bimetallic ROMP initiators [(DME)((CF3)2MeCO)2(ArN)MoCH]2-1,4-C6H4 (DME = 1,2-dimethoxyethane; la) and [(DME)((CF3)2MeCO)2(ArN)MoCHCHCH]2-1,4-C6H4 (6), respectively. An X-ray study of [(THF)((CF3)2MeCO)2(ArN)MoCH]2-1,4-C6H4 (THF = tetrahydrofuran; ib), which is closely related to la, showed it to be the expected bimetallic species in which each end is approximately a trigonal bipyramidal monoadduct of a syn alkylidene with the THF coordinated to the NOO face of the metal trans to the Mo=C bond. Treatment of la with hium-t-butoxide yielded [(Bu-t-O)2(ArN)MoCH]2-1,4-C6H4 (2). Addition of four equivalents of Me3CCH2MgCl to la produced the bimetallic species [(Me3CCH2)2(ArN)MoCH]2- 1,4-C6H4 (3), which upon treatment with 2,6diisopropylphenol generated a diastereomeric mixture of [(DME)(ArO)(Me3CCH2)(ArN)MoCH]2-1,4-C6H4 (4). The solid state structure of 3 revealed a "syn/syn" bimetallic species related to lb. In solution two resonances can be observed in the alkylidene region of the 1H NMR spectra for the "syn/anti" isomer of la, Ib, 2, 3, 4 and 5. The total amount of the "syn/anti" isomer varies between 4 and 20% of the total. Bimetallic species la, 2, and 6 initiate at both ends upon addition of less than ten equivalents of 4,5-dicarbomethoxynorbornadiene (DCMNBD),and afford homopolymers of DCMNBD and methyltetracyclododecene (MTD) in a living fashion. MALDI-TOF mass spectra of ferrocene-containing homopolymers have been obtained that are consistent with the polymerization process being living.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Chemistry

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Singh, Rojendra

Advisor dc:contributor.advisor

• Richard R. Schrock.

• Chemistry.

Statement dc:rights

• 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.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/43771

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/43771