Download or read book Investigations of Sterically Demanding Ligands in Molybdenum and Tungsten Monopyrrolide Monoalkoxide Catalysts for Olefin Metathesis written by Laura Claire Heidkamp Gerber and published by . This book was released on 2013 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 2 investigates the mechanism of the temperature-controlled polymerization of 3- methyl-3-phenylcyclopropene (MPCP) by Mo(NAr)(CHCMe 2Ph)(Pyr)(OTPP) (Ar = 2,6- diisopropylphenyl, Pyr = pyrrolide, OTPP = 2,3,5,6-tetraphenylphenoxide). Cissyndiotactic poly(MPCP) is obtained at -78 °C, while atactic poly(MPCP) is obtained at ambient temperature. The syn initiator (syn refers to the isomer in which the substituent on the alkylidene points towards the imido ligand and anti where the substituent points away) reacts with MPCP to form an anti first-insertion product at low temperatures, which continues to propagate to give cis,syndiotactic polymer. At higher temperatures, the anti alkylidenes that form initially upon reaction with MPCP rotate thermally to syn alkylidenes on a similar timescale as polymer propagation, giving rise to an irregular polymer structure. In this system cis,syndiotactic polymer is obtained through propagation of anti alkylidene species. Chapters 3 - 5 detail the synthesis and reactivity of compounds containing a 2,6- dimesitylphenylimido (NAr*) ligand in order to provide a better understanding of the role of steric hindrance in olefin metathesis catalysts. A new synthetic route to imido alkylidene complexes of Mo and W, which proceeds through mixed-imido compounds containing both NAr* and NtBu ligands, was developed to incorporate the NAr* ligand. Alkylidene formation is accomplished by the addition of 3 equivalents of pyridine*HCl to Mo(NAr*)(NBu)(CH 2CMe2Ph)2 or the addition of 1 equivalent of pyridine followed by 3 equivalents of HCl solution to W(NAr*)(N'Bu)(CH 2CMe2Ph)2 to provide M(NAr*)(CHCMe 2Ph)Cl 2(py) (py = pyridine). Monoalkoxide monochloride, bispyrrolide, and monoalkoxide monopyrrolide (MAP) compounds are isolated upon substitution of the chloride ligands. Reaction of W MAP complexes (W(NAr*)(CHCMe 2Ph)(Me2Pyr)(OR)) with ethylene allows for the isolation of unsubstituted metallacycle complexes W(N Ar*)(C 3H6)(Me 2Pyr)(OR) (R = CMe(CF 3)2, 2,6-Me2C6H3, and SiPh 3). By application of vacuum to solutions of unsubstituted metallacyclebutane species, methylidene complexes W(NAr*)(CH 2)(Me2Pyr)(OR) (R = tBu, 2,6-Me2C6H3, and SiPh 3) are isolated. Addition of one equivalent of 2,3- dicarbomethoxynorbornadiene to methylidene species allows for the observation of firstinsertion products by NMR spectroscopy. Investigations of NAr* MAP compounds as catalysts for olefin metathesis reactions show that they are active catalysts, but not E or Z selective for ring-opening metathesis polymerization the homocoupling of 1-octene or 1,3-dienes. Methylidene species W(NAr*)(CH 2)(Me2Pyr)(OR) (R = 2,6-Me 2C6H3 or SiPh3) catalyze the ring-opening metathesis or substituted norbornenes and norbornadienes with ethylene.

Download or read book Synthesis and Reactivity of High Oxidation State Tungsten and Molybdenum Olefin Metathesis Catalysts Bearing New Imido Ligands written by Jonathan Clayton Axtell and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 1 details the synthesis of tungsten imidoalkylidene compounds bearing strongly electron-withdrawing imido ligands. An alternative synthesis involving the treatment of WCl6 with 4 equivalents of N-trimethylsilyl-substituted anilines and subsequent workup with 1,2-dimethoxyethane (DME) has been employed to form complexes of the type W(NAr)2C12(dme); syntheses employing WO2C 2(dme) as the tungsten precursor were unsuccessful. Alkylation with neopentylmagnesium chloride (ClMgNp) and subsequent treatment with trifluoromethanesulfonic acid (HOTf) affords imidoalkylidene species W(NAr)(CHCMe 3)(OTf)2(dme) (OTf = trifluoromethanesulfonate); analogous neophylidene ([W]CHCMe 2Ph) species could not be made under these conditions. Treatment of these compounds with two equivalents of LiO(2,6-(CHCPh 2)C6H3)-Et2O affords the bisaryloxide complexes of the type W(NAr)(CHCMe3)(OR)2. Ring-Opening Metathesis Polymerization (ROMP) studies using a series of these bisaryloxides show that rates of ROMP increase as the electron-withdrawing power of the substituents on the imido ligand increase if steric bulk about the metal center is held constant. A similar trend between two bisaryloxides is observed for anti-to-syn alkylidene rotation rates at 50*C in toluene-d8 . Difficulties synthesizing bis-pyrrolide complexes of the type W(NAr)(CHCMe3)(pyr)2 precluded their use as catalyst precursors; some MAP species containing the more sterically encumbering 2,5-dimethylpyrrolide ligand are presented and the metathesis activity of MAP species bearing the 2,5-dimethylpyrrolide ligand is discussed. Chapter 2 introduces Mo and W complexes bearing the current extreme in sterically bulky imido ligands, the NHIPT (HIPT = 2,6-(2,4,6-iPr 3CH2)CH3) ligand, in an effort to generate all anti alkylidene species. A non-traditional synthetic route is employed in order to install this ligand first as an anilide, and after subsequent proton transfer, as an imido ligand to form a mixed imido species of the type M(NHIPT)(N'Bu)(NH'Bu)Cl. Addition of one equivalent of 2,6-lutidinium chloride, followed by alkylation affords dialkyl species M(NHIPT)(N'Bu)Np 2, and treatment with three equivalents of pyridinium chloride yields all anti imidoalkylidene dichloride species as mono-pyridine adducts, M(NHIPT)(CHCMe 3)C 2(py) (M = Mo, W). General reactivity, including strategies for removal of the pyridine adduct as well as substitution and metathesis chemistry, are discussed. ROMP of MPCP (MPCP = 3-methyl-3-phenylcyclopropene) by a Mo-based MAP species bearing the NHIPT ligand yields predominantly cis,syndiotactic poly(MPCP) and in the homo-metathesis of 1 -octene yields ~81% cis-7-tetradecene. The possible source of trans olefinic product is addressed. Chapter 3 presents the synthesis of the first (1-adamantyl)imido species of tungsten. The functional equivalent of common bisimido precursors for other Mo/W alkylidene species, [W(NAd) 2C 2(AdNH2)1 2, is shown to be a dimer stabilized by hydrogen-bonding interactions between adamantylamine protons and adjacent chlorides bound to the second metal of the dimer. Subsequent alkylation with ClMgNp affords the expected dialkyl species, and treatment with three equivalents of 3,5-lutidinium chloride affords imidoalkylidene complex W(NAd)(CHCMe 3)(C) 2(lut)2 (lut = 3,5-dimethylpyridine). The most desirable synthetic route toward monoalkoxide pyrrolide (MAP) species proceeds through a monoaryloxide monochloride intermediate W(NAd)(CHCMe 3)(Cl)(OAr)(lut) (Ar = 2,6-(2,4,6-Me 3)C6H3, 2,6-(2,4,6-'Pr 3)C6H3). Removal of lutidine with B(C6 F5 )3 and subsequent treatment with lithium pyrrolide affords W(NAd)(CHCMe3)(pyr)(OAr) (pyr = pyrrolide); 2,5-dimethylpyrrolide analogues (W(NAd)(CHCMe3)(Me2pyr)(OAr) can be accessed via protonolysis by HOAr from W(NAd)(CHCMe3)(Me2pyr)2(lut).

Download or read book High oxidation state Molybdenum and Tungsten Monoalkoxide Pyrrolide Alkylidenes as Catalysts for Olefin Metathesis written by Erik Matthew Townsend and published by . This book was released on 2014 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 1 describes work toward solid-supported W olefin metathesis catalysts. Attempts to tether derivatives of the known Z-selective catalyst W(NAr)(C3H6)(pyr)(OHIPT) (Ar = 2,6- diisopropylphenyl, pyr = pyrrolide; HIPT = 2,6-bis-(2,4,6-triisopropylphenyl)phenyl) to a modified silica surface by covalent linkages are unsuccessful due to destructive interactions between W precursors and silica. W(NAr)(C3H6)(pyr)(OHIPT) and W(NAr)(CHCMe2Ph)(pyr)(OHIPT-NMe2) (HIPT-NMe 2 = 2,6-bis-(2,4,6-triisopropylphenyl)-4- dimethylaminophenyl) are adsorbed onto calcined alumina. W(NAr)(C 3H6 )(pyr)(OHIPT) is destroyed upon binding to alumina, while W(NAr)(CHCMe 2Ph)(pyr)(OHIPT-NMe 2) appears to bind through a non-destructive interaction between the dimethylamino group and an acidic surface site. The heterogeneous catalysts perform non-stereoselective metathesis of terminal olefins, and W(NAr)(CHCMe2Ph)(pyr)(OHIPT-NMe2) can be washed off the surface with polar solvent and perform solution-phase Z-selective metathesis. Chapter 2 details selective metathesis homocoupling of 1,3-dienes with Mo and W monoalkoxide pyrrolide (MAP) catalysts. A catalytically relevant vinylalkylidene complex, Mo(NAr)(CHCHCH(CH3)2)(Me2pyr)(OHMT) (HMT = 2,6-bis(2,4,6-trimethylphenyl)phenyl; Me2pyr = 2,5-dimethylpyrrolide), is isolated. A series of Mo and W MAP catalysts is synthesized and tested for activity, stereoselectivity, and chemoselectivity in 1,3-diene metathesis homocoupling. Catalysts containing the OHIPT ligand display excellent selectivity in general, and W catalysts are less active but more selective than their Mo counterparts. Chapter 3 recounts the synthesis and characterization of several heteroatom-substituted alkylidene complexes with the formula Mo(NAr)(CHER)(Me2pyr)(OTPP) (TPP = 2,3,5,6- tetraphenylphenyl; ER = OPr, N-pyrrolidinonyl, N-carbazolyl, pinacolborato, trimethylsilyl, SPh, or PPh2). Synthesis proceeds via alkylidene exchange between Mo(NAr)(CHR)(Me2pyr)(OTPP) (R = H, CMe2Ph) and a CH2CHER precursor. Each complex behaves similarly to known MAP complexes in olefin metathesis processes; the electronic identity of ER has little effect on catalytic properties. Distinctive features of alkylidene isomerism and catalyst resting state are examined. Chapter 4 contains synthetic and catalytic studies of thiolate-containing Mo and W imido alkylidene complexes. The species M(NAr)(CHCMe 2Ph)(pyr)(SHMT) (M = Mo or W), Mo(NAr)(CHCMe2Ph)(Me2pyr)(STPP), and Mo(NAr)(CHCMe2Ph)(STPP)2 are synthesized by substitution of the appropriate thiol or thiolate ligands for pyrrolide or triflate ligands in metal precursors. These complexes show similar structural and spectral characteristics to alkoxidecontaining species. The thiolate complexes and their alkoxide analogues are compared for activity and selectivity in metathesis homocoupling and ring-opening metathesis polymerization processes. In general, thiolate catalysts are slower and less selective than alkoxide catalysts.

Download or read book Handbook of Metathesis Volume 1 written by Robert H. Grubbs and published by John Wiley & Sons. This book was released on 2015-02-23 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second edition of the Handbook of Metathesis, edited by Nobel Prize Winner Robert H. Grubbs and his team, is available as a 3 Volume set as well as individual volumes. Volume 1, edited by R. H. Grubbs together with A. G. Wenzel focusses on Catalyst Development and Mechanism. The new edition of this set is completely updated (more than 80% new content) and expanded, with a special focus on industrial applications. Written by the "Who-is-Who" of metathesis, this book gives a comprehensive and high-quality overview. It is the perfect and ultimate one-stop-reference source in this field and indispensable for chemists in academia and industry alike. View the set here - http://www.wiley.com/WileyCDA/WileyTitle/productCd-3527334246.html Other available volumes: Volume 2: Applications in Organic Synthesis, Editors: R. H. Grubbs and D. J. O ́Leary - http://www.wiley.com/WileyCDA/WileyTitle/productCd-3527339493.html Volume 3: Polymer Synthesis, Editors: R. H. Grubbs and E. Khosravi - http://www.wiley.com/WileyCDA/WileyTitle/productCd-3527339507.html

Download or read book Novel Strategies for the Synthesis of Tungsten VI and Molybdenum VI Imido Oxo Alkylidene NHC Complexes and Their Application in Ring Opening Metathesis Polymerization written by Janis Musso and published by Cuvillier Verlag. This book was released on 2022-05-12 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, the synthesis of neutral and cationic group(VI) imido/oxo alkylidene N-heterocyclic carbene (NHC) complexes that tolerate protic functional groups and aldehydes was reported. Unprecedented turnover numbers of up to 1.2 million were found for their silica-supported representatives. Some group(VI) alkylidene NHC complexes even display stability towards moisture and air. Coordination of the NHC to tungsten imido bistriflate precursor complexes, however, can lead to undesired side reactions. This work consequently aimed at the development of novel, more efficient routes to neutral and cationic tungsten imido/oxo alkylidene NHC complexes. In addition, some molybdenum imido alkylidene NHC complexes were targeted. Thereby, the scope of synthetically accessible complexes was broadened and, subsequently, their reactivity in ring-opening metathesis polymerization (ROMP) was probed. Those complexes were used as thermally latent initiators for the ROMP of dicyclopentadiene. Precise determination of the onset temperature of polymerization was achieved via monitoring with differential scanning calorimetry. Furthermore, the selectivity of novel complexes was tested for the formation of stereoregular polymers through ROMP of enantiomerically pure norbornene derivatives, which allowed for the synthesis of up to 98% trans-isotactic or cis-syndiotactic polymers depending on the steric demand of the imido and the alkoxide ligand.

Download or read book Longer lived Olefin Metathesis Catalysts Based on Molybdenum and Ruthenium written by Joseph Yoon and published by . This book was released on 2020 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of olefin metathesis has seen considerable growth in the recent past. Some of the earliest milestones in the field include the synthesis of well-defined catalysts based on molybdenum, tungsten, and ruthenium. The efficiencies of these catalysts, however, are limited by their decomposition. Efforts have been made to increase the lifetime of these catalysts by changing the ligand sphere, to stabilize catalytic intermediates. Examples include the employment of the N-heterocyclic carbene (NHC) and the chelating (o-isopropoxy)benzylidene ligand seen in the second-generation Grubbs and Hoveyda catalysts. Processes that utilize the olefin metathesis processes, like those in the petroleum industry and large-scale production of chemicals, are bound by the need for high catalyst loadings which translate to high costs. The work herein presents the pursuit of longer-lived olefin metathesis catalysts based on molybdenum and ruthenium. The first goal of this thesis project was to develop a stable molybdenum-based olefin metathesis catalyst supported by a tridentate PONOP ligand and a chelating (o- x methoxy)benzylidene ligand. Previous attempts in our lab employed nonchelating alkylidene initiators - yielding no success in isolation. The rationale behind this design was that a chelating ether moiety will stabilize the molybdenum-center enough to be isolable. Attempts to isolate the chelating molybdenum-alkylidene species were also unsuccessful. Instead, we probed the in-situ ROMP of norbornene using iPrPONOP MoCl3 as a precatalyst and (2-methoxybenzyl)magnesium chloride as a cocatalyst. This cocatalyst did not lend any improvements to the simpler nonchelating Grignard cocatalysts. The synthesis of a novel dialkyl zirconocene complex is also reported. The second and more heavily pursued endeavor was the development of longer-lived ruthenium olefin metathesis catalysts. Specifically, we aimed at improving the second-generation Hoveyda catalyst with the use of a hemilabile tridentate NHC ligand. Two novel catalysts bearing NHC ligands with a hemilabile ethoxy-pyridyl arm were synthesized along with their unique organic frameworks. The catalyst containing the 2,6-diisopropylphenyl group (C1-Me) was investigated more comprehensively because it was more readily prepared. This complex was characterized by high thermal stability under metathesis conditions and remarkable TONs in the self-metathesis of 1-decene. In our efforts to prepare C1-Me without utilizing a Grubbs I intermediate, a new complex (6) bearing our NHC ligand was isolated and characterized by 1H NMR and single crystal x-ray diffraction spectroscopy. The reaction of C1-Me with ethylene did not produce the desired C1-Me-methylidene variant - however, the same reaction with propylene gave C1-Me-ethylidene with relative ease. Analyzing the active catalytic species under the metathesis of 1-decene revealed that the resting state of the catalyst is not the expected methylidene, but rather the longer chain nonylidene. xi Initiation studies were conducted to compare the rates of initiation for catalyst C1-Me and the nonmethylated C1-H. First, the rate of metathesis was followed in the irreversible reaction with ethyl vinyl ether. Second, ligand exchange equilibrium experiments were carried out to compare the dissociation constants for the pyridyl moieties in both catalysts. The outcome of these studies revealed that catalyst C1-Me, with a methyl group in the phenoxide ring, exhibits a 10-fold increase in initiation versus the nonmethylated C1-H catalyst. The NHC ligand scaffold reported in this work may assist in the development of other inorganic and organometallic catalytic systems, as many rely on the use of ancillary ligands for support. Furthermore, fixing a hemilabile ethoxy-pyridyl arm onto already robust systems, such as ruthenium catalysts bearing a cyclic alkyl amino carbene ligand, may offer even greater catalytic turnover numbers (TONs).

Download or read book The Evolution of Molybdenum and Tungsten Olefin Metathesis Catalysts written by Annie Jinying Hannah King and published by . This book was released on 2010 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 with90% 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).

Download or read book Iron and Molybdenum Complexes Supported by Pincer Ligands written by Steven Ryan Ruark and published by . This book was released on 2016 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since its discovery in the mid 1950’s, olefin metathesis has become one of the most widely used chemical reactions. Olefin metathesis involves the breaking of carbon-carbon double bonds and the redistribution of the fragments to form new olefins by way of a metal alkylidene.6 It is used in industry to convert cheap plant oils into useful products such as alpha olefins, jet fuel and green diesel. The Elevance BioRefinery has the capacity to run this reaction and produce up to 400 million pounds of products per year. The most expensive part in this refinery process is the catalyst itself. The catalyst currently used is an alkylidene complex of ruthenium—an expensive and rare metal. This has led the Schrodi group to explore the possibility of developing catalysts based on abundant and cheap metals such as iron or molybdenum.40,41 We first attempted to support iron with a tridentate pincer ligand, OiPrPONOP, however the ligand was not robust enough and more than one ligand was required to adequately protect the iron xv center. Ultimately, the ligand was reacted with Fe(PMe3)4 to make (OiPrPONOP)Fe(PMe3)2. This complex is very stable and unreactive, preventing its transformation into any catalytic species. We then turned our attention to a pincer OCO-NHC ligand. This ligand was able to stabilize an iron tricyclohexyphosphine complex, (OC-NHC)FePCy3, However, attempts to react this complex with diazo compounds to form an iron alkylidene (OCO-NHC)Fe=CHR were unsuccessful. Further studies focused on replacing the PCy3 ligand with pyridines, in an attempt to make the complex more labile. However, the resulting species proved much too sensitive to water and was difficult to isolate and characterize. Inspired by the research done by the Chirik group where they reduced several arylpyridinediimine ( ArPDI) ironII complexes into a reduced N2-bridged complex. They reported the bound N2 molecules would readily exchange with 15N2 and ultimately they were able to form an iron alkylidene complex. However, the complex was not metathesis active.54,42 We successfully reduced MesPDIFeBr2 into the bis-N2 complex but the complex refused to react cleanly in attempts to make iron alkylidene species. We also explored the possibility of forming a molybdenum alkylidene supported by a tridentate iPrPONOP ligand. After successfully forming iPrPONOPMoCl3 we tried several strategies to form and isolate a molybdenum alkylidene. We attempted a similar reduction as the iron species trying to access a bis-N2 bridged molybdenum complex but the reaction resulted in decomposition of the complex. We then attempted ‘Schrock type’ chemistry by reacting the iPrPONOPMoCl3 complex with Grignard reagents.81 However, this strategy resulted in decomposition as well. We successfully performed ring opening metathesis polymerization (ROMP) of norbornene by adding Grignard reagents to several different tridentate supported MoCl3 precatalysts. Select polymers were then analyzed for cis content by 1 H NMR to probe for serioregularity. The only precatalyst to have more than 50% cis content was the BinapthPONOPMoCl3 / methyl- and trimetylsilylmethlyl-Grignard reagents but only when run at 25 °C. xvi We were able to perform ROMP of dicyclopentadiene (DCPD) with the molybdenum complex / Grignard reagents. However, while the fully polymerized product is extremely hard and transparent we could only achieve a soft nontransparent product, indicating incomplete polymerization.

Download or read book Metathesis Polymerization written by Michael R. Buchmeiser and published by Springer. This book was released on 2010-02-12 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 1 T.W. Baughman, K.B. Wagner: Recent Advances in ADMET Polymerization.- 2 G. Trimmel, S. Riegler, G. Fuchs, C. Slugovc, F. Stelzer: Liquid Crystalline Polymers by Metathesis Polymerization.- 3 M.R. Buchmeiser: Regioselective Polymerization of 1-Alkynes and Steroselective Cyclopolymerization of alpha, omega -Heptadiynes.

Download or read book Hydrogen Transfer Reactions written by Gabriela Guillena and published by Springer. This book was released on 2016-09-27 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry Collections presents critical reviews from the journal Topics in Current Chemistry organized in topical volumes. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.

Download or read book Stimulating Concepts in Chemistry written by Fritz Vögtle and published by John Wiley & Sons. This book was released on 2000 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fresh ideas have always been a necessary ingredient for progress in chemistry. Without a continuous supply of stimulating ideas from creative researchers, there would be no new insights into the subject. But what are some of the ideas that pervade modern chemistry? The answer to this question is to be found in "Stimulating Concepts in Chemistry". In a collection of 24 essays, a group of leading researchers provides an overview of the most recent developments in their fields. Readers can find out about modern concepts in chemistry such as self-assembly, nanochemistry, and molecular machines. Moreover, many spectacular advances have been achieved from the fusion of chemistry with life and materials science - a development which is illustrated by contributions on enzyme mimics, molecular wires, and chemical sensors. Further, the essayists write about new nanomaterials, efficient methods in synthesis, and big biomolecules - indeed, many of the topics that have dominated some of the recent discussions in chemistry. This outstanding text makes use of a special layout to reflect the editors' aim of presenting concepts in the form of essays. Thus, the book is not merely another source of knowledge but is intended to stimulate readers to develop their own ideas and concepts. This format should help to make the book interesting to a wide range of scientists. Students of chemistry will benefit from the different style of presentation of their subject, while researchers in industry and academia will welcome the exciting way in which some of the most challenging concepts in modern chemistry are presented.

Download or read book Olefin Metathesis and Metathesis Polymerization written by K. J. Ivin and published by Elsevier. This book was released on 1997-01-07 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a follow-up to Ivins Olefin Metathesis, (Academic Press, 1983). Bringing the standard text in the field up to date, this Second Edition is a result of rapid growth in the field, sparked by the discovery of numerous well-defined metal carbene complexes that can act as very efficient initiators of all types of olefin metathesis reaction, including ring-closing metathesis of acyclic dienes, enynes, and dienynes; ring-opening metathesis polymerizationof cycloalkenes, acyclic diene metathesis polymerization; and polymerization of alkynes, as well as simple olefin metathesis. Olefin Metathesis and Metathesis Polymerization provides a broad, up-to-date account of the subject from its beginnings in 1957 to the latest applications in organic synthesis. The book follows the same format as the original, making it useful toteachers and to researchers, and will be of particular interest to those working in the fields of organic chemistry, polymer chemistry, organometallic chemistry, catalysis, materials science and chemical engineering. Discusses different classes of olefin metathesis and the choice of reaction conditions and catalyst Considers commercial processes with examples from existing and new technologies Provides a complete overview of the subject from its beginning to the present day

Download or read book Site Selective Catalysis written by Takeo Kawabata and published by Springer. This book was released on 2016-02-23 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry presents critical reviews of the present and future trends in modern chemical research. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science.The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience.Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.Review articles for the individual volumes are invited by the volume editors.Readership: research chemists at universities or in industry, graduate students

Download or read book Handbook of Metathesis 3 Volume Set written by Robert H. Grubbs and published by John Wiley & Sons. This book was released on 2015-05-26 with total page 1639 pages. Available in PDF, EPUB and Kindle. Book excerpt: Covering the complete breadth of the olefin metathesis reaction. The second edition of the ultimate reference in this field is completely updated and features more than 80% new content, with the focus on new developments in the field, especially in industrial applications. No other book covers the topic in such a comprehensive manner and in such high quality, and this new edition retains the three-volume format: Catalyst Development, Applications in Organic Synthesis and Polymer Synthesis. Edited by a Nobel laureate in the field, and with a list of contributors that reads like a "Who's-Who" of metathesis, this is an indispensable one-stop reference for organic, polymer and industrial chemists, as well as chemists working with organometallics. Individual volumes also available separately to purchase Volume 1: Catalyst Development - http://www.wiley.com/WileyCDA/WileyTitle/productCd-3527339485.html Volume 2: Applications in Organic Synthesis - http://www.wiley.com/WileyCDA/WileyTitle/productCd-3527339493.html Volume 3: Polymer Synthesis - http://www.wiley.com/WileyCDA/WileyTitle/productCd-3527339507.html

Download or read book Asymmetric Catalysis written by B. Bosnich and published by Springer. This book was released on 2011-09-26 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rate of advance in areas of science is seldom constant. Usually certain fields effloresce with activity because of the ~ealization that solutions are possible to long standing important problems. So it is now with asymmetric catalysis, a field which promises to change profoundly the strategic thinking of synthetic chemists. As this Report will show, reagents which can induce catalytic enantiocontrol of chemical transformations could represent the ultimate synthetic method. Nearly all synthetic strategies of complex molecules involve steps which require enantiocontrol and, in many cases, a specific catalytic transformation embodying enan tiocontrol has enormous advantages in terms of the rate and economy of the reaction. Because asymmetric catalysis is in a formative stage, workers with different backgrounds have joined the field. This Workshop had representatives with organometallic, organic, structural, kinetic, enzymatic, microbiological and industrial backgrounds. Each had his own perspective and this Report represents a consensus of this group of eleven people. The result is probably as compre hensive and balanced a view of the subject as is possible at present. It is hoped that those who have until now had but a glancing interest in asymmetric catalysis will find this Report a useful indication of its present state. We believe that asymmetric catalysis will have an increasing impact on the development of chemistry and will eventually dominate much of synthetic and industrial chemistry.

Download or read book Annual Energy Outlook 2011 with Projections To 2035 written by Energy Information Administration (U.S.) and published by Government Printing Office. This book was released on 2011-06-14 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: The projections in the Energy Information Administration's (EIA) Annual Energy Outlook 2011 (AEO2011) focus on the factors that shape the U.S. energy system over the long term. Under the assumption that current laws and regulations remain unchanged throughout the projections, the AEO2011 Reference case provides the basis for examination and discussion of energy production, consumption, technology, and market trends and the direction they may take in the future. It also serves as a starting point for analysis of potential changes in energy policies. But AEO2011 is not limited to the Reference case. It also includes 57 sensitivity cases (see Appendix E, Table E1), which explore important areas of uncertainty for markets, technologies, and policies in the U.S. energy economy. Key results highlighted in AEO2011 include strong growth in shale gas production, growing use of natural gas and renewables in electric power generation, declining reliance on imported liquid fuels, and projected slow growth in energy-related carbon dioxide (CO2) emissions even in the absence of new policies designed to mitigate greenhouse gas (GHG) emissions. AEO2011 also includes in-depth discussions on topics of special interest that may affect the energy outlook. They include: impacts of the continuing renewal and updating of Federal and State laws and regulations; discussion of world oil supply and price trends shaped by changes in demand from countries outside the Organization for Economic Cooperation and Development or in supply available from the Organization of the Petroleum Exporting Countries; an examination of the potential impacts of proposed revisions to Corporate Average Fuel Economy standards for light-duty vehicles and proposed new standards for heavy-duty vehicles; the impact of a series of updates to appliance standard alone or in combination with revised building codes; the potential impact on natural gas and crude oil production of an expanded offshore resource base; prospects for shale gas; the impact of cost uncertainty on construction of new electric power plants; the economics of carbon capture and storage; and the possible impact of regulations on the electric power sector under consideration by the U.S. Environmental Protection Agency (EPA). Some of the highlights from those discussions are mentioned in this Executive Summary. Readers interested in more detailed analyses and discussions should refer to the "Issues in focus" section of this report. I

Download or read book Stereoselective Polymerization with Single Site Catalysts written by Lisa S. Baugh and published by CRC Press. This book was released on 2007-11-29 with total page 698 pages. Available in PDF, EPUB and Kindle. Book excerpt: New synthetic techniques allow chemists to modify polymer microstructures more precisely than ever, making it possible to design materials that meet increasingly demanding performance requirements. Written and edited by experts in the field, Stereoselective Polymerization with Single-Site Catalysts reviews how the relative stereochemistry of