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Showing 1 to 20 of 33 for “"Sterically demanding"”.
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The synthesis of sterically demanding ligands and examples of their copper complexes
… in roughly 24 hours, with the more sterically demanding substrates requiring altered conditions. Typical isolated yields are in excess of 70%. Moreover, methyl- and aryl-substituted pyrrolyl anions have been shown to display similar chemistry using 5.0 mol% Pd(OAc)₂. Though they …
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Synthesis and reactivity of vanadium and niobium complexes containing sterically demanding amido ligands
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1998.
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Synthesis and reactivity of early transitional metal complexes supported by sterically demanding amido ligands
Chapter 1: Ligand Synthesis Strategies -- Chapter 2: Early Transition Metal Complexes of Bidentate N[R]ArL, o-Dimethylamino- N-tert-Butylanilide -- Chapter 3: Three-Coordinate Molybdenum(III) Complexes: Synthesis, Properties, and Nitrogen Atom Transfer Thereto -- Chapter 4: The …
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Investigations of sterically demanding ligands in molybdenum and tungsten monopyrrolide monoalkoxide catalysts for olefin metathesis
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 …
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Controlling the reactivity of Mo(III) with di- and tri-atomic molecules via sterically demanding ligands
Chapter 1. Molybdenum Dinitrogen Chemistry: Formation and Reactivity of (Ar[tBu]N)3MoN2- A collection of (Ar[tBu]N)3MoN2- compounds, supported with Na+, K+, Mg2+ and Ca2+ have been prepared through a variety of synthetic routes. In several experiments, N2 was replaced with other small molecules to …
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Vanadium and chromium complexes supported by sterically demanding ligands : studies relevant to the reduction of dinitrogen to ammonia
Chapter 1. Using the [HIPTN3N]3- ligand ([HIPTN3N]3- = [(HIPTNCH2CH2)3N]3-; HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3 = HexaIsoPropylTerphenyl), green paramagnetic [HIPTN3N]V(THF) (1) can be prepared from VCl3(THF)3. Reduction of 1 with potassium graphite in ethereal solvents yields a highly sensitive red …
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Synthesis and reactivity of early transition metal "Frustrated Lewis Pairs"
… of "Frustrated Lewis Pairs" (FLP) wherein sterically demanding Lewis acids and bases do not interact in the expected donor-acceptor fashion, but rather exhibit unique reactivity. To date this concept of FLPs has been limited to main group systems. In this thesis we demonstrate that Lewis …
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Catalytic Activity of Molybdenum-Dioxo Complexes
… ligand environment. The smaller electronically demanding ligand environment showed readily rapid reactivity for aromatic diols, but competitive side reactions and catalyst dimerization occurred. The more sterically demanding ligand environment was observed to slow the relative reaction times, …
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Steric and Electronic Effects Induced by Ancillary Ligand Substitutions on Cyclopentadienyl Osmium Complexes
… [(C5Me5)Os(dmpm)H2+] showed that C5Me5 is more sterically demanding than C 5H5, as evidenced by the 7--8° decrease in the dihedral angle between the P-Os-P and C5 ring planes for the C5H 5 analogue, suggesting that movement of the phosphine toward the less sterically bulky C5 ring may lead …
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Synthesis and stabilities of mononuclear iron (II) dicarbonyls derived from neutral NNS ligands : structural models of the apo-active site of mono-iron (Hmd) hydrogenase
… Reactions under similar conditions with more sterically demanding ligands (R = quinoline (Q), chlorophenyl (ClPh)) afford a complex salt of the form (([subscript R]NNS)Fe(CO)₂Br)(Fe(CO)₃(Br)₃). Complexes have been characterized using X-ray crystallography, IR spectroscopy and low temperature …
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Catalytic C-N and C-F bond formation by organometallic group 11 complexes
… of internal alkynes with Et3N*3HF (Chapter 2). Sterically demanding, electrophilic supporting ligands and the presence of acid buffers improve reaction efficiency. A study of aryl-substituted alkynes suggests that electron-poor aryl groups favor shorter reaction times and higher regioselectivity …
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Chiral phosphonyl and thiophosphonyl carbanions in asymmetric alkylation and olefination reactions
… (83/17-85/15) was observed except in the case of sterically demanding group (R = $\rm C(C\sb2H\sb5)\sb3)$ where high diastereoselectivity (95/5) could be accomplished. An extremely high level of asymmetric induction was achieved in the alkylation of (l)-N-isopropyloxazaphosphorinane-2-oxide with a …
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Part I: Mechanistic Insight in Alkyl-Alkyl and Aryl-Aryl Negishi Cross-Coupling Part II: Large Scale Synthesis of NHC Precursors: 2,6-DI(3-Pentyl) Aniline and 2,6-DI (4-Heptyl) Aniline
… and efficient method for the preparation of sterically demanding Pd PEPPSI-IPent, IPentCl, IHept, and IHeptCl pre-catalysts are presented and the results of optimization for the multi-gram synthesis of 2,6-disubstituted anilines is discussed.
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Studies of Metathesis for Materials Applications: Present and Future Possibilities
… in synthesis of diblock copolymers from sterically demanding and sterically unencumbered monomers. Work on alkyne metathesis sought to expand existing understanding of the features that influence stability and reactivity in ruthenium carbynes. A classification system was developed in …
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Development of Deactivation-Resistant Catalysts for Pd-Catalyzed C–N Cross-Coupling Reactions
… set of five-membered heteroaryl halides with sterically demanding α-branched cyclic amines and acyclic secondary amines are reported for the first time. The key to the broad applicability of this method is the synergistic combination of (1) the moderate-strength base NaOTMS, which limits …
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Phenylene Vinylene Based Supramolecular Materials: Triblock Rodcoil Molecules and Highly Branched Amphiphiles
… materials, triphenyl amine moietiesare the most sterically demanding residues in the triblock molecules system. These rodcoil molecules showed convincingly that architecture is far more important than any specific chemical sequence in determining nanostructure formation. More recently, a series …
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Use of sterically hindered carboxylate ligands to model structural and functional features of dioxygen-activating centers in non-heme diiron enzymes
… Shifts in Diiron(II) Complexes Supported by Sterically Hindered Carboxylate Ligands General synthetic routes are described for a series of diiron(II) complexes supported by sterically demanding carboxylate ligands 2,6-di(p-tolyl)benzoate (ArTolCO2-) and 2,6-di(4-fluorophenyl)benzoate …
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OPPORTUNITIES AND CHALLENGES OF BIOCATALYSIS IN PHARMACEUTICAL SCIENCES: DEVELOPING TAILORED BIOCATALYSTS FOR SYNTHETIC APPLICATIONS
… variants with an expanded substrate scope toward sterically demanding amines. Directed evolution efforts aimed at improving asymmetric amination are currently ongoing. Overall, this work highlights how biocatalysis is consolidating its role as an essential resource in modern synthetic chemistry. …
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Exploiting cooperative effects in s-Block organometallics for new applications in synthesis and catalysis
… base, which combines within the same molecule a sterically demanding β-diketiminate ligand with a kinetically activatedTMP base [DippNacnacMg(TMP)], regioselective magnesiation of heterocyclic and aromatic molecules, including pyrazine or 1,2,4,5-tetrafluorobenzene, can be achieved at room …
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The synthesis, characterisation and photochemistry of novel organometallic complexes
… by replacing aluminium chloride by the more sterically demanding Lewis acid, diethylaluminium chloride. All attempts at using organic fulgides as diene or enone ligands with a series of metals has shown them to be totally unsuitable for this purpose. We succesfully synthesised a wide range of …
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