Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Vita.Includes bibliographical references.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(cont.) 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 NMR spectra are consistent with it being Mo(NAr)(CH-t-Bu)NpCl; it decomposed bimolecularly upon attempted isolation. The other Mo(NR)Np3Cl species were found to be more stable than Mo(NAr)Np3C1, but when they did decompose at elevated temperatures, no neopentylidene complex could be observed. Addition of neopentyllithium to Mo(NR)Np3CI species (R = Ar, CPh3, or Ad) yielded Mo(NR)(CH-t-Bu)Np2 species, the adamantylimido version of which is unstable toward bimolecular decomposition. Addition of I equivalent of 2,6-diisopropylphenol, 2,6-dimethylphenol, or 3,5-(2,4,6-i-Pr3C6H2)2C6H30H (HIPTOH) to Mo(NCPh3)(CH-t-Bu)Np2 led to formation of Mo(NCPh3)(CH-t-Bu)Np(OR) species, while treatment of Mo(NCPh3)(CH-t- Bu)Np2 with C6FsOH gave Mo(NCPh3)Np3(OC6Fs). The three monophenoxide neopentylidene complexes showed metathesis activity for ring-closing a small selection of amines and an ether. X-ray studies were completed for Mo[N-3,5-(CF3)2C6H3]C14(THF), Mo[N-3,5-(CF3)2C6H3]Np3CI, Mo(NCPh3)Np3CI, and Mo(NCPh3)(CH-t-Bu)Np(OHIPT).(cont.) Addition of I equivalent of 2,6-diisopropylphenol, 2,6-dimethylphenol, or 3,5-(2,4,6-i-Pr3C6H2)2C6H30H (HIPTOH) to Mo(NCPh3)(CH-t-Bu)Np2 led to formation of Mo(NCPh3)(CH-t-Bu)Np(OR) species, while treatment of Mo(NCPh3)(CH-t- Bu)Np2 with C6FsOH gave Mo(NCPh3)Np3(OC6Fs). The three monophenoxide neopentylidene complexes showed metathesis activity for ring-closing a small selection of amines and an ether. X-ray studies were completed for Mo[N-3,5-(CF3)2C6H3]C14(THF), Mo[N-3,5-(CF3)2C6H3]Np3CI, Mo(NCPh3)Np3CI, and Mo(NCPh3)(CH-t-Bu)Np(OHIPT).(cont.) Chapter 3. Reactions of Mo Bispyrrolide Complexes with Enantiomerically Pure Diols: In Situ Catalyst Generation and Studies of Olefin Metathesis Reactions In the Fume Hood. Reactions of bispyrrolide molybdenum complexes Mo(NAd)(CHCMe2Ph)(pyr)2 and Mo(N-2-6-i-Pr2C6H3)(CHCMe2Ph)(pyr)2 with (R)-BiphenH2, and (R)-Benz2BitetH2 were examined (pyr = C4H4N, Benz2BitetH2 = 3,3'-dibenzhydryl-5,5',6,6',7,7',8,8'-octahydro-1,1'- binaphthyl-2,2'-diol). The resulting in situ generated catalysts were studied in three olefin metathesis reactions. These systems were found to be as active and enantioselective as the analogous isolated complexes. When the stock solutions of Mo(NAd)(CHCMe2Ph)(pyr)2, Mo(N- 2,6-i-Pr2C6H3)(CHCMe2Ph)(pyr)2, (R)-BiphenH2, and (R)-Benz2BitetH2 were stored in the fume hood over a period of one month, the in situ prepared catalysts were determined to be nearly identical in terms of their catalytic properties to the catalysts generated in situ in the glovebox.by Tatiana Pilyugina.Ph.D
