Download or read book Synthesis and Reactivity of Iron Complexes Supported by a Bulky Bis pyrrolyl pyridine Pincer Ligand and Iridium Catalyzed Borylation of Methane written by Kyle T. Smith and published by . This book was released on 2016 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pincer Compounds written by David Morales-Morales and published by Elsevier. This book was released on 2018-04-11 with total page 756 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pincer Compounds: Chemistry and Applications offers valuable state-of-the-art coverage highlighting highly active areas of research—from mechanistic work to synthesis and characterization. The book focuses on small molecule activation chemistry (particularly H2 and hydrogenation), earth abundant metals (such as Fe), actinides, carbene-pincers, chiral catalysis, and alternative solvent usage. The book covers the current state of the field, featuring chapters from renowned contributors, covering four continents and ranging from still-active pioneers to new names emerging as creative strong contributors to this fascinating and promising area. Over a decade since the publication of Morales-Morales and Jensen’s The Chemistry of Pincer Compounds (Elsevier 2007), research in this unique area has flourished, finding a plethora of applications in almost every single branch of chemistry—from their traditional application as very robust and active catalysts all the way to potential biological and pharmaceutical applications. Describes the chemistry and applications of this important class of organometallic and coordination compounds Includes contributions from global leaders in the field, featuring pioneers in the area as well as emerging experts conducting exciting research on pincer complexes Highlights areas of promising and active research, including small molecule activation, earth abundant metals, and actinide chemistry
Download or read book Late Transition metal Complexes Supported by Pincer Ligands written by Wilson D. Bailey and published by . This book was released on 2016 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: Late transition-metal pincer complexes of primarily palladium(II) and platinum(II) have been investigated for their application as catalysts in partial oxidation reactions. The epoxidation of higher olefins using molecular oxygen as the oxidant has been targeted, and the individual reaction steps needed to accomplish this overall transformation are described herein, including: (1) hydrogenolysis of a metal hydroxide (M-OH) species to yield a metal hydride (M-H), (2) insertion of O2 into the M-H bond to form a metal hydroperoxide (M-OOH), and (3) O-atom transfer from the M-OOH to epoxides, yielding a M-OH and completing the catalytic cycle. Previous results from our group on these individual transformations using (tBuPCP)Pd and (tBuPCO)Pd fragments are also reviewed. The requirements for O2 insertion into PdII and PtII hydrides are discussed. An array of cationic, neutral, and anionic Pd-H and Pt-H complexes supported by a tBuPNP backbone were synthesized and evaluated for O2 insertion (tBuPNP = 2,6-bis-(di-tbutylphosphinomethyl)pyridine). Metal-ligand cooperation was observed in the activation of H2 to form neutral hydride complexes. The effect of ligand protonation/deprotonation on the trans influence experienced by the hydride ligand was investigated. No reaction with O2 was observed with the cationic hydrides, while the neutral and anionic forms reacted with O2 at the tBuPNP backbone. The synthesis and characterization of mono- and dinuclear Pd-OH complexes supported by a PCNR pincer ligand (PCNR = (1-(3-((di-tert-butylphosphino)methyl)phenyl)-1H-5-R-pyrazole), R = H, Me) is presented. When R = H, ligand pyrazole "rollover" C-H activation was observed, forming a mixed ligand (PCNH)Pd(μ-OH)Pd(PCC) dinuclear structure. This "rollover" was investigated using DFT computations. The mono- and dinuclear hydroxide species were evaluated for hydrogenolysis. The dinuclear compounds {[(PCNR)Pd]2(μ-OH)}[OTf] reacted under an H2 atmosphere to yield the corresponding dinuclear hydrides {[(PCNR)Pd]2(μ-H)}[OTf]. A mechanistic study on the hydrogenolysis of the μ-bridged hydroxide {[(PCNMe)Pd]2(μ-OH)}[OTf] revealed first order kinetics in both [Pd] and [H2]. Terminal hydrides were not detected, and reduction of the mononuclear hydroxide complexes (PCNR)Pd-OH to Pd0 was observed under H2. The reduction was proposed to proceed through displacement of the pyrazole arm, and was examined by DFT computations. Lastly, a new strategy to promote O-atom transfer from M-OOH to epoxides, the final step in the targeted catalytic cycle, is proposed. Preliminary studies on NNNPyz, NNNEt, and NNMe ligated PdII and PtII are discussed (NNNPyz = 2,6-bis(5-tbutyl-1H-pyrazol-3-yl)pyridine; NNNEt = 2-(5-tbutyl-1H-pyrazol-3-yl)-6-(diethylaminomethyl)pyridine; NNMe = 2-(5-tBu-1H-pyrazol-3-yl)-6-methylpyridine). The NNNPyz ligand, containing two acidic sites in proximity to the fourth site in the square plane, was found to protonate M-O2 complexes, chelate to the metal center and oxidize phosphine substrates. Similar reactivity was observed with NNNEt and NNMe, however hemilability of these ligands resulted in undesired coordination modes.
Download or read book Synthesis and Reactivity of a N pyrrolyl Bis imino pyridine Cobalt Complex written by Damon A. Mclean and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rhodium and Iridium Pincer Complexes Supported by Bis phosphino silyl Ligation written by Erin Morgan and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Pincer Metal Complexes written by Akshai Kumar and published by Elsevier. This book was released on 2021-11-11 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pincer-Metal Complexes: Applications in Catalytic Dehydrogenation Chemistry provides an overview of pincer-metal catalytic systems that transform hydrocarbons and their derivatives from an synthetic and mechanistic point-of-view. This book provides thorough coverage of the operating mechanisms and dehydrogenation catalyst compatibility in both functionalized and unfunctionalized hydrocarbon systems. In addition, it includes success stories of pincer-metal systems, as well as current and future challenges. The book is an ideal reference for researchers practicing synthetic organic chemistry, inorganic chemistry, organometallic chemistry and catalysis in academia and industry. In recent years there has been a surge in the research on hydrocarbon dehydrogenation catalytic systems that are compatible with polar substituents. This helps facilitate formulation of tandem processes that are not limited to hydrocarbon transformation but also to hydrocarbon functionalization in a single pot. Covers applications of pincer-metal complexes in organic transformations Includes pincer-group 8 and 9 metal complexes for alkane dehydrogenations Features a discussion of pincer-metal complexes for the dehydrogenation of functionalized hydrocarbons and electro-catalytic transformations
Download or read book Iridium Complexes in Organic Synthesis written by Luis A. Oro and published by John Wiley & Sons. This book was released on 2008-12-03 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ranging from hydrogenation to hydroamination, cycloadditions and nanoparticles, this first handbook to comprehensively cover the topic of iridium in synthesis discusses the important advances in iridium-catalyzed reactions, namely the use of iridium complexes in enantioselective catalysis. A must for organic, complex and catalytic chemists, as well as those working with/on organometallics.
Download or read book Reduced Bis Imino pyridine Iron and Manganese Complexes written by Sarah Kathleen Russell and published by . This book was released on 2011 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: The synthesis, electronic structures and reactivity of bis(imino)pyridine iron and manganese complexes were investigated. A series of dimeric bis(imino)pyridine iron dinitrogen compounds was prepared by reduction of the corresponding iron dihalide complexes with sodium naphthalenide. The dinitrogen compounds were shown to have electronic structures similar to the monomeric bis(imino)pyridine iron bis(dinitrogen) compound, (iPrPDI)Fe(N2). Evaluation of the catalytic olefin hydrogenation activity of the new dinitrogen compounds revealed a significant improvement in rate over (iPrPDI)Fe(N2), which was attributed to the smaller substituents on the bis(imino)pyridine aryl groups. The reactivity of the bis(imino)pyridine iron dinitrogen compounds with diazoalkanes was investigated. For all of the iron dinitrogen compounds, diazoalkane N-N bond cleavage was observed with monosubstituted diazoalkanes. Addition of diphenyldiazomethane to smaller bis(imino)pyridine iron dinitrogen compounds furnished bis(imino)pyridine iron carbene complexes. A combination of 1H NMR, Mössbauer and X-ray absorption spectroscopies, SQUID magnetometry and X-ray diffraction was used to propose several possible electronic structures for the bis(imino)pyridine iron carbene complexes. The spectroscopic data most strongly supported an electronic structure having an intermediate spin iron(III) center and a one-electron reduced bis(imino)pyridine chelate. The bis(imino)pyridine iron carbene complexes underwent carbene transfer to carbon monoxide and aryl azides, but not cyclopropanation or olefin metathesis reactions. The bis(imino)pyridine iron dinitrogen compounds were also found to be competent catalysts for carbon-carbon bond forming catalysis. Addition of ethylene to butadiene in the presence of 5 mol% iron catalyst resulted in a [2[pi] + 2[pi]] cycloaddition to furnish vinylcyclobutane, while addition of ethylene to isoprene under the same conditions resulted in 1,4hydrovinylation to yield 5-methyl-1,4-hexadiene. Under similar reaction conditions, [(MePDI)Fe(N2)]2([mu]2-N2) also catalyzed the cycloisomerization of 1,5-hexadiene. Finally, syntheses of variations of the bis(imino)pyridine iron dinitrogen compounds were investigated. Reduction of a bis(aldimino)pyridine iron dibromide did not afford an iron dinitrogen compound, but instead gave a diiron compound. Modeling variable temperature SQUID data for this compound provided experimental evidence for the redox activity of the bis(aldimino)pyridine ligand. The reduction of a bis(imino)pyridine manganese dichloride also did not afford a dinitrogen complex, but instead resulted in a bis(tetrahydrofuran) compound.
Download or read book Olefin Polymerization written by Walter Kaminsky and published by Wiley-VCH. This book was released on 2006-08-18 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an enormous velocity, olefin polymerization has expanded to one of the most significant fields in polymers since the first industrial use about 50 years ago. In 2005, 100 million tons of polyolefins were produced - the biggest part was catalyzed by metallorganic compounds. The Hamburg Macromolecular Symposium 2005 with the title "Olefin Polymerization" involved topics such as new catalysts and cocatalysts, kinetics, mechanism and polymer reaction engineering, synthesis of special polymers, and characterization of polyolefins. The conference combined scientists from different disciplines to discuss latest research results of polymers and to offer each other the possibility of cooperation. This is reflected in this volume, which contains invited lectures and selected posters presented at the symposium.
Download or read book Synthesis and Reactivity of Rhodium and Iridium Complexes Supported by New Silyl Pincer Ligands written by MacLean Darren F. and published by . This book was released on 2008 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bis imino pyridine Iron and Cobalt Complexes written by Amanda Catherine Bowman and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The synthesis, reactivity and electronic structures of a series of bis(imino)pyridine iron and cobalt complexes was investigated. A series of monomeric bis(imino)pyridine cobalt dinitrogen complexes was investigated using a combination of 1H NMR and infrared spectroscopies, X-ray crystallography, EPR spectroscopy, solution and solid state magnetic measurements and density functional theory. The neutral bis(imino)pyridine cobalt dinitrogen complexes have doublet ground states and are best described as low-spin cobalt(I) centers with an unpaired electron on the singly reduced chelate, while the anionic bis(imino)pyridine cobalt dinitrogen complexes are also best described as low-spin cobalt(I) centers with dianionic chelates. These investigations established that reduction of monochloride precursors occurs at the metal center, in contrast to the related bis(imino)pyridine iron bis(dinitrogen) complex, (iPrPDI)Fe(N2)2, where reduction of the chelate is observed. A series of bis(imino)pyridine iron imide complexes was also investigated. A combination of Xray crystallography, variable temperature SQUID magnetization data and Mössbauer spectroscopy was used to elucidate the electronic structures of these complexes. In contrast to the previously reported N-aryl substituted bis(imino)pyridine iron imide complexes, where an iron(III) metal center and a singly reduced chelate was observed, an iron(IV) metal center and a triplet diradical chelate was observed for N-alkyl substituted bis(imino)pyridine iron imide complexes. For (iPrPDI)FeN(2Ad) (iPrPDI = 2,6-(2,6-iPr2-C6H3-N=CMe)2C5H3N), thermal spin crossover from S = 0 to S = 1 was observed when warming from 15 K to 200 K. (ArPDI)FeNR compounds with an S = 0 ground state promoted C-H bond activation of both imine methyl groups of the bis(imino)pyridine ligand. The C-H bond activation with (iPrPDI)FeN(CyOct) was firstorder in iron with a rate constant of k = 3.4(2)x10-5 s-1 at 25 °C and a primary kinetic isotope effect of 3.3(2), consistent with a rate-determining step of intramolecular C-H bond activation. In contrast, no C-H bond activation of the ligand was observed for the iron imide complexes that are S = 1 at 23 °C. The reactivity of bis(imino)pyridine iron imide compounds with hydrogen, silanes, terminal alkynes and organic azides, and the electronic structures of the resulting iron complexes, was also investigated.
Download or read book Synthesis and Reactivity of Thioether supported Organoiron and Low valent Iron Complexes and Cyanide bridged Binuclear Complexes written by Michael T. Mock and published by ProQuest. This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of FeCl 2 (THF) 1.5 lead to the synthesis of [PhTt tB u]FeCl that provided entry into new [PhTt tBu]FeX chemistry. [PhTt tBu]FeCl crystallizes as a five-coordinate chloride bridged dimer that is a high-spin ferrous complex with an S = 2 ground state. The metathetical reaction of [PhTt tBu]FeCl with the desired dialkylmagnesium reagent, R 2 Mg (R = Me, Et, Ph, Bn), in 1,4-dioxane/THF leads to the formation of high-spin, S = 2, electronically and coordinatively unsaturated four-coordinate organoiron(II) complexes of the type, [PhTt tBu]Fe(R) (R = Me, Et, Ph, Bn). Reaction of [PhTt tBu]Fe(R) (R = Me, Et, Ph) with CO yields the low-spin, S = 0, six-coordinate complexes [PhTt tBu]Fe(CO) 2 (R) (R = Me, Et, Ph). Carbonylation of [PhTt tBu]Fe(Bn) yields [PhTt tBu]Fe(CO) 2 (Bn) and the reduced monovalent species [PhTt tBu]Fe(CO) 2 . The reduction of [PhTt tBu]FeCl in the presence of a phosphine ligand, PMe 3 or PEt 3, yields the high-spin, S = 3/2, monovalent iron complexes, [PhTt tBu]Fe(PMe 3) or [PhTt tBu]Fe(PEt 3) in moderate yields. [PhTt tBu]Fe(PMe 3) reacts with CO producing the low-spin, S = 1/2, monovalent product [PhTt tBu]Fe(CO) 2 . X-ray crystallographic analysis confirms a five-coordinate, square pyramidal coordination geometry. [PhTt tBu]Fe(PMe 3) reacts with diphenylacetylene producing the high-spin, S = 3/2 product [PhTt tBu]Fe(PhC=CPh). X-ray crystallography confirms a five-coordinate, square pyramidal coordination geometry with PhC=CPh bound to the iron center in a symmetric, side-on eta 2 binding mode. [PhTt tBu]Fe(PMe 3) reacts with adamantyl azide producing the high-spin, S = 3/2 product, [kappa 2 -PhTt tBu]Fe(N 4 Ad 2). The dialkyltetraazadiene ligand exhibits nearly identical N-N bonds suggesting a delocalized ligand radical dialkyltetraazadiene resonance form. Efforts to model a catalytically inhibited form of COdH were performed by designing a simple Ni:Fe binuclear complex that provides the essential metal coordination spheres of the C-cluster active site. The scope of these studies was expanded to include a series of cyanide-bridged binuclear complexes, ('S 3 ')Ni-CN-M[Tp tBu] (M = Fe, Co, Ni, Zn). A similar coupling scheme was used to synthesize the copper(I) analogue, Et 4 N{('S 3 ')Ni-CN-Cu[Tp tBu]}. Two synthetic strategies were employed to investigate the formation of cyanide-bridged linkage isomers. The products of two different 13 CN labeled reactions intended to yield ('S 3 ')Ni-CN-Zn[Tp tBu] and ('S 3 ')Ni-NC-Zn[Tp tBu] were analyzed. Nearly identical infrared and 13 C NMR spectroscopic data provide additional evidence that ('S 3 ')Ni-CN-Zn[Tp tBu] is produced in both reactions.
Download or read book Terdentate Iron Complexes written by Aaron Maurice Tondreau and published by . This book was released on 2011 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: A three-electron series of four-coordinate bis(imino)pyridine iron nitrosyl complexes was synthesized. The electronic structure of this series of compounds was determined by the use of X-ray crystallography, Mössbauer, IR, NMR, and EPR spectroscopies, and corroborated by DFT calculations. (iPrPDI)Fe(NO) was determined to be an intermediate-spin ferric complex with a triplet two electron reduced bis(imino)pyridine chelate and a triplet NO-. The overall spin state of (iPrPDI)Fe(NO) is S = 1/2. The oxidation of (iPrPDI)Fe(NO) occurs at the bis(imino)pyridine chelate, and the electronic structure of the iron nucleus remains intermediate-spin ferric. The reduction of (iPrPDI)Fe(NO) also is bis(imino)pyridine chelate centered. This yields a three-electron reduced chelate, leaving the iron intermediate-spin ferric and the nitrosyl as NO-. The reduction and oxidation of compounds was carried out to yield two other three-electron series. The synthesis and characterization of [Li(OEt2)3][(iPrPDI)Fe(CH2CMe3)(N2)], (iPrPDI)Fe(CH2CMe3), and [(iPrPDI)Fe(CH2CMe3)][BPh4] allowed for the determination of the degree of chelate participation over a three-electron series pertinent to olefin polymerization. The redox events were shown to occur at the bis(imino)pyridine chelate, leaving the iron nucleus Fe(II) throughout the series. [Na15-Crown-5][(iPrPDI)Fe(CO)2], (iPrPDI)Fe(CO)2, and [(iPrPDI)Fe(CO)2][BArF24] were also synthesized. Analysis of [(iPrPDI)Fe(CO)2][BArF24] indicates that oxidation of the formally Fe(0) complex (iPrPDI)Fe(CO)2 results in the oxidation of the bis(imino)pyridine chelate to a neutral ligand, giving a formally Fe(I) species. [Na-15Crown-5][(iPrPDI)Fe(CO)2] was not structurally characterized, but EPR spectroscopy indicates that the reduction occurred at the ligand, and the iron is low spin Fe(II). Bis(imino)pyridine iron complexes also were utilized as catalysts for the hydrosilylation of ketones, aldehydes, and olefins. The hydrosilylation of ketones and aldehydes was performed with primary and secondary silanes using bis(imino)pyridine iron dialkyl complexes and pybox iron dialkyls. The hydrosilylation of olefins was performed with tertiary silanes utilizing several reduced bis(imino)pyridine iron complexes. The result was reactivity that proved to be competitive with platinum based catalysis. In several instances iron outperformed platinum in terms of selectivity and fewer side-products.
Download or read book Synthesis of Chromium Iron and Nickel Complexes Using Aryl based Chelates as Ancillary Ligands and a Series of Bis alpha iminopyridyl Iron Compounds with Varying Donor Ligands written by Emily C. Volpe and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several classes of aryl-based chelates containing pyridine, oxazoline, or imine donors and their reactivity with 1st-row transition metals were investigated in light of the potential of carbon-based ligands to impart strong ligand fields. Heterolytic C-H bond activation of 2-phenylpyridine was achieved with Ni(OTf)2. The cyclometalated product and its derivatives undergo substitution, insertion, and additional cyclometalation reactions. Aryl-oxazolines display a range of reactivity patterns which are dependent on the reaction conditions, the metal, and the particular ligand employed. Aryl-aryl coupling, oxazoline ring-opening, and methylene deprotonation were examined, but were tangential to the goal of making metal-aryl bonds. Successful arylation of nickel, iron and chromium was accomplished using a methylated benzyl-oxazoline aryl anion, and the spectroscopic, structural, and magnetic properties of these complexes are described. Tridentate arylpyridylimines or diarylimines undergo facile arylation with cis-(Me3P)4Fe(Me)2 to give low-spin, sixcoordinate iron compounds. Their thermal and oxidation behavior are studied, and the spectroscopic properties of their azaallyl derivatives are compared to previouslyreported, related species. A highly-fluorinated congener of the diarylimine iron complexes was sought, and preliminary evidence of its divergent reactivity is noted. Finally, a series of iminopyridine complexes of the formula (N,N'-[alpha]- iminopyridyl)2Fe(L/X)n have been examined by X-ray and Mossbauer spectroscopy. The redox-active nature of the iminopyridine ligands and the donating ability of the additional L/X ligands have been assessed.
Download or read book Rhodium and Iridium Complexes Supported by Chelating Bis N heterocyclic Carbene Ligands written by Roxy Joanne Lowry and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Eighty-five percent of all industrial chemical processes occur catalytically. The world's expanding appetite for mass production of exotic chemicals necessitates the design and application of enhanced catalysts. To optimize catalytic materials, the detailed relationships between catalyst architecture and reactivity must be determined. Although for many ligand families these relationships are well understood, novel catalysts require in depth empirical investigation to determine these connections. The design of a novel di-N-heterocyclic carbene family of ligands in reported herein. These C2 symmetric ligands are based on the rigid 9,10-dihydro-9,10-ethanoanthracene backbone and designed for utilization in chiral catalysis. Thorough investigation into the relationships between the ligand's structure and the architecture of the resulting rhodium and iridium catalysts directed the design of three generations of our novel ligand family. The first generation, trans-1,1'-[9,10-dihydro-9,10-ethanoanthracene-11,12- diyldimethanediyl]bis(benzylimidazole) bis(triflouromethansulfonate) [DEAM-BI](OTf)2 (2-1), is too flexible to enforce a rigid chiral pocket about a metal center under catalytic conditions. The constrained second generation ligands, trans-1,1'-(9,10-dihydro-9,10-ethanoanthracene.
Download or read book Synthesis and Reactivity of Me4PCP and Me4POCOP Iridium Complexes written by Travis T. Lekich and published by . This book was released on 2018 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes new syntheses of [superscript]Me4 PCP and [superscript]Me4 POCOP pincer ligands ([superscript]R4PCP = 1,3-bis(dialkylphosphinomethyl)-benzene; R4POCOP = 1,3-bis(dialkylphosphinito)-benzene), and the coordination chemistry of the corresponding iridium complexes. Bis(dimethyl)phosphine ligands have been difficult to synthesize because their precursors are expensive or dangerous to obtain. As such, they have not been as extensively studied as the larger [superscript]R4PCP (R = [superscript]t Bu, [superscript]i Pr) derivatives. Chapter 2 shows that aminophosphines, which can be safely synthesized on large scales, are excellent precursors to bis(dimethyl)phosphine ligands: Me4PCP, Me4POCOP, and DMPE. Iridium complexes of [superscript]Me4 PCP and [superscript]Me4 POCOP show similar and novel reactivity compared to that of larger analogs (R = [superscript]t Bu, [superscript]i Pr). Chapter 3 illustrates the steric environment of ([superscript]Me4 PCP)Ir(CO) through structure and reactivity comparisons. Chapter 4 describes the facile nature of H2 addition to (Me4PCP)Ir(CO) and subsequent isomerization. The nature of this reaction allowed us to investigate the isomerization mechanism and revealed that the isomerization likely proceeds through a CO insertion pathway. Chapter 4 also reports the surprising reactivity of DCM and silver acetate with ([superscript]Me4 PCP)Ir(CO), which likely is facilitated by the ligand’s reduced steric profile.
