2026-09-19T12:53:25Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/362622026-06-11T14:03:51Zcom_1721.1_7582com_1721.1_7581col_1721.1_131022
Richard R. Schrock.
Sinha, Amritanshu
Massachusetts Institute of Technology. Dept. of Chemistry.
Massachusetts Institute of Technology. Department of Chemistry
2008-02-28T16:28:23Z
2008-02-28T16:28:23Z
2006
2006
http://hdl.handle.net/1721.1/36262
77461790
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.
Vita.
Includes bibliographical references.
The attempted syntheses of molybdenum imido alkylidene complexes of the type Mo(NArc,)(CH-t-Bu)[Biphen] and Mo(N-2-CF3C6H4)(CHCMe2Ph)[Biphen] (Biphen2 = 3,3'-di-t-butyl-5,5',6,6'-tetramethyl- 1,1'-biphenyl-2,2'-diolate) from Mo(NArcl)(CH-t-Bu)(OTf)2(dme) and [Biphen]K2 have sporadically afforded mixtures containing the desired products along with the corresponding amido alkylidyne complexes, Mo(NHArcl)(C-t-Bu)[Biphen] and Mo(NH-2-CF3C6H4)(CCMe2Ph)[Biphen], respectively. The reaction of [Biphen]K2 with Mo(NArc,)(CH-t-Bu)(OTf)2(dme) and 10 equivalents of triethylamine reproducibly gave Mo(NHArc,)(C-t-Bu)[Biphen] in 40% yield. An X-ray crystal structure of a related complex, Mo(NHArc,)(CCMe2Ph)[S-Biphen] confirmed the proposed structure and also revealed that one ortho chloride approaches within 2.93 A of the metal approximately trans to the alkylidyne ligand. Attempts to prepare three other amido alkylidyne complexes in an analogous manner from Mo(NR")(CH-t-Bu)(OTf)2(dme) (NR" = N-2-CF3C6H4, N-2,6-i-Pr2C6H5, N-2,6-Me2C6H5) with [Biphen]K2 in the presence of 10-20 equivalents of triethylamine failed.
(cont.) Chapter 2 The reaction between Mo(NAr)(CH-t-Bu)(CH2-t-Bu)2 (Ar = 2,6-i-Pr2C6H3) and various alcohols (1-AdamantylOH, t-BuOH, ArOH, (CF3)2CHOH, (CF3)2MeCOH, (CF3)3COH, C6F5OH) in pentane or toluene yielded either complexes of the type Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OR) through direct addition of ROH across a Mo-C bond, or complexes of the type Mo(NAr)(CH2-t-Bu)3(OR) through direct addition of ROH across a Mo=C bond. The trineopentyl species appear to be formed when the alcohol has a relatively low pKa. The outcome also can depend upon whether the alcohol is employed neat, or in benzene, and mixtures are observed in some circumstances. The conversion of Mo(NAr)(CH2-t-Bu)3(OR) into Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OR) was shown to be unimolecular in several examples. Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OR) complexes have been found to be surprisingly active catalysts for various metathesis reactions. In contrast, M(NAr)(CH-t-Bu)(CH2-t-Bu)2 species are virtually inactive for metathesis. X-ray structures are reported for Mo(NAr)(CH2-t-Bu)3(OC6F5), Mo(NAr)(CH-t-Bu)(CH2-t-Bu)IOSi(O-t-Bu)3], [Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OC6F)12, and Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OC6F5)(PMe3).
(cont.) Chapter 3. Complexes of the type Mo(NR")(CHR')(N(R)3,5-C6H3Me2)2 (NR" = N-2,6-i-Pr2C6H, N-2,6-Me2C6Hs; R' = t-Bu, CMe2Ph; R' = i-Pr, t-Bu) and Mo(NR")(CHR')(NR2)2 (NR" = N-2,6-i-Pr2C6H,, N-2,6-Me2C6H5; R' = t-Bu, CMe2Ph; R = Me, Ph) can be isolated as orange-red solids in 30-35% yields or oils by reacting Mo(NR")(CHR')(OTf)2(dme) with LiN(R')(3,5-C6H3Me2)(ether) or with LiNR2. The synthesis of Mo(NR")(CHCMe2Ph)(NPh2)2 can be improved to 70-90% isolated yields when Mo(NR")(CHCMe2Ph)[OCMe(CF3)212 is used with LiNPh2(ether). Mo(NAr)(CHCMe2Ph)(NPh2)2 has been crystallographically characterized. Mo(NR")(CHR')(N(R)3,5-C6H3Me2)2 species reacted with t-BuOH and Me(CF3)2COH in benzene to give Mo(NR")(CHR')(OR)2 (OR = O-t-Bu, OCMe(CF3)2) in situ. However, no reactions of Mo(NR")(CHR')(N(R')3,5-C6H3Me2)2 were observed with enantiomerically pure diols such as [R-TRIP]H2 (3,3'-2,4,6-i-Pr3C6H2-binaphthol), [R-Ph]H2 (3,3'-C6H5-binaphthol), [rac-Mesitylbinap]H2 (3,3'-2,4,6-Me3C6H2-binaphthol) and [R-TMSbinapJH2 (3,3'-SiMe3-binaphthol).
(cont.) Bisamido complexes of the type Mo(NR")(CHR')(NPh2)2 were found to react with the aforementioned alcohols and diols to give Mo(NR")(CHR')(diolate) species in situ, which were further reacted in a catalytic fashion with two substrates to give the corresponding ring-closed products. Preliminary :results of the in situ catalysis demonstrated here compare fairly well with the analogous catalytic reactions reported with isolated catalysts. Appendix A. Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OC6F5) (Ar = 2,6-i-Pr2C6H3) can be reacted with 5-10 equivalents of trans-3-hexene to give a crystallographically characterized dimeric complex, [Mo(NAr)(CH2-t-Bu)(OC6F5)]2 that contains an unbridged Mo=Mo bond (2.410(8) A) in high yields. The above complex can also be prepared by treating Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OC6F5) with 0.5 equivalents of divinylbenzene. IMo(NAr)(CH2-t-Bu)(OC6F5)]2 will slowly catalyze the metathesis reactions of simple substrates, although less than 5% of the catalyst seems to be activated in such reactions.
(cont.) It was observed that catalytically active species for metathesis reactions can be generated by another Mo (d2) species, Mo(NArcl)(Biphen)(H2C=CH2)(ether) (NArc, = N-2,6-C12C6H3, Biphen2 = 3,3'-di-t-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'-diolate) that could effect the ring-opening metathesis polymerization of norbornene. A mixture of Mo(NArcl)(Biphen)(H2C=CH2)(ether) and 20 equivalents of diallylether in benzene-d6 when treated with 10 equivalents of norbornene gives 54% conversion to dihydrofuran in 10 days.
by Amritanshu Sinha.
Ph.D.
176 leaves
eng
Massachusetts Institute of Technology
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
Chemistry.
Synthesis of molybdenum olefin metatheses catalysts through protonation reactions
Synthesis of olefin metathesis catalysts through protonation reactions
Thesis
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<Title>Synthesis of molybdenum olefin metatheses catalysts through protonation reactions</Title>
<Subtitle>Synthesis of olefin metathesis catalysts through protonation reactions</Subtitle>
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<Abstract>The attempted syntheses of molybdenum imido alkylidene complexes of the type Mo(NArc,)(CH-t-Bu)[Biphen] and Mo(N-2-CF3C6H4)(CHCMe2Ph)[Biphen] (Biphen2 = 3,3'-di-t-butyl-5,5',6,6'-tetramethyl- 1,1'-biphenyl-2,2'-diolate) from Mo(NArcl)(CH-t-Bu)(OTf)2(dme) and [Biphen]K2 have sporadically afforded mixtures containing the desired products along with the corresponding amido alkylidyne complexes, Mo(NHArcl)(C-t-Bu)[Biphen] and Mo(NH-2-CF3C6H4)(CCMe2Ph)[Biphen], respectively. The reaction of [Biphen]K2 with Mo(NArc,)(CH-t-Bu)(OTf)2(dme) and 10 equivalents of triethylamine reproducibly gave Mo(NHArc,)(C-t-Bu)[Biphen] in 40% yield. An X-ray crystal structure of a related complex, Mo(NHArc,)(CCMe2Ph)[S-Biphen] confirmed the proposed structure and also revealed that one ortho chloride approaches within 2.93 A of the metal approximately trans to the alkylidyne ligand. Attempts to prepare three other amido alkylidyne complexes in an analogous manner from Mo(NR")(CH-t-Bu)(OTf)2(dme) (NR" = N-2-CF3C6H4, N-2,6-i-Pr2C6H5, N-2,6-Me2C6H5) with [Biphen]K2 in the presence of 10-20 equivalents of triethylamine failed.</Abstract>
<Abstract>(cont.) Chapter 2 The reaction between Mo(NAr)(CH-t-Bu)(CH2-t-Bu)2 (Ar = 2,6-i-Pr2C6H3) and various alcohols (1-AdamantylOH, t-BuOH, ArOH, (CF3)2CHOH, (CF3)2MeCOH, (CF3)3COH, C6F5OH) in pentane or toluene yielded either complexes of the type Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OR) through direct addition of ROH across a Mo-C bond, or complexes of the type Mo(NAr)(CH2-t-Bu)3(OR) through direct addition of ROH across a Mo=C bond. The trineopentyl species appear to be formed when the alcohol has a relatively low pKa. The outcome also can depend upon whether the alcohol is employed neat, or in benzene, and mixtures are observed in some circumstances. The conversion of Mo(NAr)(CH2-t-Bu)3(OR) into Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OR) was shown to be unimolecular in several examples. Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OR) complexes have been found to be surprisingly active catalysts for various metathesis reactions. In contrast, M(NAr)(CH-t-Bu)(CH2-t-Bu)2 species are virtually inactive for metathesis. X-ray structures are reported for Mo(NAr)(CH2-t-Bu)3(OC6F5), Mo(NAr)(CH-t-Bu)(CH2-t-Bu)IOSi(O-t-Bu)3], [Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OC6F)12, and Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OC6F5)(PMe3).</Abstract>
<Abstract>(cont.) Chapter 3. Complexes of the type Mo(NR")(CHR')(N(R)3,5-C6H3Me2)2 (NR" = N-2,6-i-Pr2C6H, N-2,6-Me2C6Hs; R' = t-Bu, CMe2Ph; R' = i-Pr, t-Bu) and Mo(NR")(CHR')(NR2)2 (NR" = N-2,6-i-Pr2C6H,, N-2,6-Me2C6H5; R' = t-Bu, CMe2Ph; R = Me, Ph) can be isolated as orange-red solids in 30-35% yields or oils by reacting Mo(NR")(CHR')(OTf)2(dme) with LiN(R')(3,5-C6H3Me2)(ether) or with LiNR2. The synthesis of Mo(NR")(CHCMe2Ph)(NPh2)2 can be improved to 70-90% isolated yields when Mo(NR")(CHCMe2Ph)[OCMe(CF3)212 is used with LiNPh2(ether). Mo(NAr)(CHCMe2Ph)(NPh2)2 has been crystallographically characterized. Mo(NR")(CHR')(N(R)3,5-C6H3Me2)2 species reacted with t-BuOH and Me(CF3)2COH in benzene to give Mo(NR")(CHR')(OR)2 (OR = O-t-Bu, OCMe(CF3)2) in situ. However, no reactions of Mo(NR")(CHR')(N(R')3,5-C6H3Me2)2 were observed with enantiomerically pure diols such as [R-TRIP]H2 (3,3'-2,4,6-i-Pr3C6H2-binaphthol), [R-Ph]H2 (3,3'-C6H5-binaphthol), [rac-Mesitylbinap]H2 (3,3'-2,4,6-Me3C6H2-binaphthol) and [R-TMSbinapJH2 (3,3'-SiMe3-binaphthol).</Abstract>
<Abstract>(cont.) Bisamido complexes of the type Mo(NR")(CHR')(NPh2)2 were found to react with the aforementioned alcohols and diols to give Mo(NR")(CHR')(diolate) species in situ, which were further reacted in a catalytic fashion with two substrates to give the corresponding ring-closed products. Preliminary :results of the in situ catalysis demonstrated here compare fairly well with the analogous catalytic reactions reported with isolated catalysts. Appendix A. Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OC6F5) (Ar = 2,6-i-Pr2C6H3) can be reacted with 5-10 equivalents of trans-3-hexene to give a crystallographically characterized dimeric complex, [Mo(NAr)(CH2-t-Bu)(OC6F5)]2 that contains an unbridged Mo=Mo bond (2.410(8) A) in high yields. The above complex can also be prepared by treating Mo(NAr)(CH-t-Bu)(CH2-t-Bu)(OC6F5) with 0.5 equivalents of divinylbenzene. IMo(NAr)(CH2-t-Bu)(OC6F5)]2 will slowly catalyze the metathesis reactions of simple substrates, although less than 5% of the catalyst seems to be activated in such reactions.</Abstract>
<Abstract>(cont.) It was observed that catalytically active species for metathesis reactions can be generated by another Mo (d2) species, Mo(NArcl)(Biphen)(H2C=CH2)(ether) (NArc, = N-2,6-C12C6H3, Biphen2 = 3,3'-di-t-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'-diolate) that could effect the ring-opening metathesis polymerization of norbornene. A mixture of Mo(NArcl)(Biphen)(H2C=CH2)(ether) and 20 equivalents of diallylether in benzene-d6 when treated with 10 equivalents of norbornene gives 54% conversion to dihydrofuran in 10 days.</Abstract>
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