Molybdenum alkylidene complexes : syntheses and applications to olefin metathesis reactions

Chapter 1. Alkylimido Molybdenum Complexes: Synthesis, Characterization and Activity as Chiral Olefin Metathesis Catalysts. Molybdenum olefin metathesis catalysts that contain previously unexplored aliphatic 1- phenylcyclohexylimido (PhCyN) and 2-phenyl-2-adamantylimido (PhAdN) groups were prepared and shown to be efficient and selective in a variety of olefin metathesis reactions. Five catalysts, Mo(NR)(CHCMe2Ph)[(S)-Biphen], Mo(NR)(CHCMe2Ph)[(R)-Trip](THF) (R = 1- adamantyl, PhCy, PhAd; Biphen = 3,3'-di-tert-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'- diolate; Trip = 3,3'-bis(2,4,6-triisopropylphenyl)- 1,1'-binaphthyl-2,2'-diolate) and Mo(NAd)(CHCMe2Ph)[(R)-Trip](THF) (Ad = I-adamantyl), were synthesized. Their catalytic activity and enantioselectivity in desymmetrization reactions such as ring-closing metathesis of amines and lactams and ring-opening/cross metathesis of a substituted norborneol with styrene were compared to the results obtained with the only known alkylimido catalyst, Mo(NAd)(CHCMe2Ph)[(S)-Biphen]. The new catalysts prove to be similar to Mo(NAd)(CHCMe2Ph)[(S)-Biphen] in the majority of the studied reactions, and the examined catalysts show overall improvement in activity and enantioselectivity compared to the traditional arylimido catalysts. Chapter 2. Synthesis of Molybdenum Imido Alkyl and Alkylidene Complexes from Molybdenum Imido Tetrachlorides. Several new Mo(NR)C14(THF) species (R = C6F5, 3,5-(CF3)2C6H3, Ad, CPh3, and 2,6-i- Pr2C6H3) were prepared via the treatment of MoC14(THF)2 with azides, and then alkylated with neopentyl reagents. Addition of Mo(NR)C14(THF) complexes in toluene to a cold solution of NpMgCl in ether gave Mo(NR)Np3Cl species (R = CFs5, 3,5-(CF3)2C6H3, Ad, Ph3C, and 2,6-i- Pr2C6H3 (Ar); Np = CH2-t-Bu) in poor (35 %) to modest (51 %) yields. Heating Mo(NAr)Np3C1 in C6D6 to 50 OC results in a-hydrogen abstraction to give neopentane and a molecule whose

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Pilyugina, Tatiana

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/1721.1/40289

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/40289