The evolution of molybdenum and tungsten olefin metathesis catalysts
Name
655319341-MIT.pdf
Description
Full printable version
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105.69 MB
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Checksum (MD5)
7bf9421a5b80d16b9e909a5f88de318a
Author(s)
King, Annie Jinying Hannah
Advisor(s)
Richard R. Schrock.
Alternative Title
Evolution of Mo and T olefin metathesis catalysts
Date Issued
2010
Publisher
Massachusetts Institute of Technology
Abstract
Chapter 1: Reaction of Mo(NR)(CHR')(OTf)2(dme) (R = 2,6-i-Pr2C6H3 (Ar), 2,6-Me2C6H3 (Ar'), 2,6-Cl2C6H3 (ArCl), 1-adamantyl (Ad); R' = CMe2Ph, CMe3; dme = dimethoxyethane) with the lithium salt of ArCl-nacnac ([2,6-Cl2C6H3NC(Me)]2CH), led to complexes of the type Mo(NR)(CHCMe2R')(OTf)(ArCl-nacnac). Treatment of these compounds with Na{BArF 4} (ArF = 3,5-(CF3)2C6H3) afforded rare examples of cationic imido alkylidene complexes, {Mo(NR)(CHR')(OTf)(ArCl-nacnac)}{BArF 4}. Addition of {HNMe2Ph}{BArF 4} to Mo(NR)(CHR')(L)2 (L = NC4H4 (Pyr), 2,5-Me2NC4H2 (Me2Pyr)) in THF produced {Mo(NR)(CHR')(L)(THF)x}{BArF 4} (x = 2 for Me2Pyr or 3 for Pyr). Addition of alcohol or phenol to {Mo(NAr)(CHCMe2Ph)(Pyr)(THF)3}{BArF 4} produced {Mo(NAr)(CHCMe2Ph)(OR")(THF)x}{BArF 4} (R" = CMe(CF3)2 (x = 2 or 3), Ar (x = 1), Ad (x = 2)). Complexes Mo(NAr)(CHCMe2Ph)(MesPyr)2 (MesPyr = 2- mesitylpyrrolide), Mo(NAd)(CHCMe3)(MesPyr)2, and Mo(NAr)(CHCMe2Ph)(OTf)(BinaphPPh2) (BinaphPPh2 = (R)-2'-(diphenylphosphino)- [1,1'-binaphthalen]-2-oxide) were also generated. The solid-state structures of Mo(NAr)(CHCMe2Ph)(OTf)(ArCl-nacnac), {Mo(NAr)(CHCMe2Ph)(ArClnacnac)}{ BArF 4}, {Mo(NAr)(CHCMe2Ph)(Pyr)(THF)3}{BArF 4}, {Mo(NAr)(CHCMe2Ph)(OCMe(CF3)2)(THF)3}{BArF 4}, {Mo(NAr)(C2H4)(OCMe(CF3)2)(THF)3}{BArF 4}, {Mo(NAr)(CH2CMe2Ph)(OAr)2}{BArF 4}, Mo(NAr)(CHCMe2Ph)(MesPyr)2, and Mo(NAr)(CHCMe2Ph)(OTf)(BinaphPPh2) have been determined by X-ray diffraction. The initial reactivity with simple olefins employing many of these new alkylidenes was explored. Chapter 2: Two diastereomers of the MAP (monoaryloxidepyrrolide) species, W(NAr)(CH2)(Me2Pyr)(OBitetBr2) (OBitetBr2 = (R)-3,3'-dibromo-2'-(tertbutyldimethylsilyloxy)- 5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthyl-2-olate), were generated through addition of HOBitetBr2 to W(NAr)(CH2)(Me2Pyr)2. The unsubstituted tungstacyclobutane species, W(NAr)(C3H6)(Me2Pyr)(OBitetBr2), was isolated by exposing the methylidene species to ethylene. A variety of NMR experiments were carried out on the methylidene and metallacycle to elucidate the exchange process between these species. Neophylidene W(NR)(CHCMe2Ph)(Me2Pyr)(OTPP) (OTPP = 2,3,5,6-tetraphenylphenoxide), methylidene W(NR)(CH2)(Me2Pyr)(OTPP), and 6 tungstacyclobutane W(NR)(C3H6)(Me2Pyr)(OTPP) were prepared. Treatment of W(NAr)(CH2)(Me2Pyr)(OTPP) with PMe3 yielded yellow W(NAr)(CH2)(Me2Pyr)(OTPP)(PMe3). NMR studies on compounds W(NAr)(C3H6)(Pyr)(OHIPT) (OHIPT = 2,6-bis-(2,4,6-triisopropylphenyl)phenoxide) and Mo(NAr)(C3H6)(Pyr)(OHIPT) were carried out to examine the exchange process between the metallacyclobutane and the methylidene. Compounds W(NAr)(C3H6)(Me2Pyr)(OBitetBr2), W(NAr)(CH2)(Me2Pyr)(OTPP), W(NAr)(CH2)(Me2Pyr)(OTPP)(THF), W(NAr)(CH2)(Me2Pyr)(OTPP)(PMe3), W(NAr)(C3H6)(Me2Pyr)(OTPP), Mo(NAr)(CH2)(Pyr)(OHIPT), Mo(NAd)(CHCMe3)(Pyr)(OHIPT), and W(NAr)(C3H6)(Pyr)(OHIPT) were crystallographically characterized. Chapter 3: Molybdenum and tungsten catalysts of the type M(NR)(CHR')(Pyr)(OR'') were prepared for highly Z-selective homocoupling metathesis of terminal olefins. Substrates screened were: 1-hexene, 1-octene, allylbenzene, allyltrimethylsilane, methyl-9-decenoate, methyl- 10-undecenoate, allylboronic acid pinacol ester, allylbenzylether, allyltosylamide, Nallylaniline, allyloxy(tert-butyl)dimethylsilane, and allylcyclohexane. Homocoupled products were isolated in moderate yields employing <1 mol% catalyst loading and with >90% Z-selectivity. Chapter 4: Exposing Mo(NAr)(C2H4)(MesPyr)2 to two equivalents of HOCH(CF3)2 afforded Mo(NAr)(C2H4)(OCH(CF3)2)2(Et2O). Mo(NAr)(C2H4)(OCH(CF3)2)(Et2O) was shown to isomerize and metathesize olefins such as propene, 1-hexene, and 1-octene at elevated temperatures. Evidence of isomerization and olefin metathesis was also observed with complexes Mo(NAd)(C2H4)(Pyr)(OHIPT) and Mo(NAr)(C2H4)(Me2Pyr)(OAr).
Description
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2010.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Subjects
Chemistry.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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