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Showing 1 to 20 of 67 for “"carbenes"”.
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Matrix Isolation of Aryl(trifluoromethyl)carbenes, Heteroaryl(trifluoromethyl)carbenes and Phenylbis(trifluoromethyl)carbenes
… for the first time. Thenaphthyl(trifluoromethyl)carbenes are photostable and have triplet ground states in matrices asmost of the other studied ary(trifluoromethyl)carbenes. The 1- and 2-naphthyl(trifluoromethyl)diazirines, the precursors of 1- and 2-naphthyl(trifluoromethyl)carbenes, have …
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The rearrangement of cyclopropyl carbenes
… studies on the rearrangement of cyclopropyl carbenes, generated by the decomposition of the p-toluene sulphonyl hydrazones of<br/>cyclopropyl aldehydes and ketones at 135 - 140° in an alkaline aprotic medium.<br/><br/>Cyclopropane carboxaldehyde p-toluene sulphonyl hydrazone itself gives rise …
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Time-Resolved Studies of Aryl Carbenes
… nm to 640 nm probe) was used to study three aryl carbenes generated by photolysis of their parent diazo compounds in fluid solution. Irradiation of 9-diazofluorene generates a transient with an absorption maximum at 470 nm which is believed to be triplet fluorenylidene. The rate constant for …
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Fluoroalkoxy-functionalized carbenes for main group and transition metal complexes
… activation. Chapter 1 reviews the background of carbenes as ligands for main group compounds and transition metal complexes. The history and development of chelating Martin-type fluoroalkoxy ligands to form unique bonding architectures is covered. The synthetic strategies employed to …
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Introduction of a Novel Family of Bitopic N-Heterocyclic Carbenes
… and a decrease in cost. N-heterocyclic carbenes (NHCs) have been recognized as a powerful class of ligands to metals, perhaps most notably in catalysis. This thesis introduces a family of bis-NHC ligands. This family links the N-alkylated benzimidazolium moieties by a bridge providing a …
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Photochemistry of 5-Membered Heteroaryl(trifluoromethyl)carbenes in Low Temperature Matrices
… and benzoxazolyl(trifluoromethyl)carbenes in low temperature N2 matrices. The 3-benzothienyl(trifluoromethyl)carbene rearranged to several new reactive intermediates such as bicyclic intermediate, ring expanded carbene and spiro product, which were not observed or characterized …
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Coordination Chemistry of Fe–S Clusters Supported by N-Heterocyclic Carbenes
… metal sites (here, monodentate N-heterocyclic carbenes), to obtain [Fe₄S₄] clusters for which subsequent reactivity can be localized to a single Fe site. That is, the steric bulk of di-aryl NHC ligands enables isolation of [Fe₄S₄] clusters in which three of the Fe centers are coordinated to …
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Structure and Reactivity of Aryl Carbenes and Aryl Nitrenes: Experimental and Computational Approaches
Part one. Three isomeric aryl carbenes, 1,8-diaza-9-fluorenylidene (18DFL), 3,6-diaza-9-fluorenylidene (36DFL), and 4,5-diaza-9-fluorenylidene (45DFL) were generated by photolyses of their corresponding diazo compounds. The physical and chemical behaviors of the diazo compounds and carbenes were …
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Self-Assembled Monolayers of N-Heterocyclic Carbenes on Gold and Silver: Applications in Biosensing
… group has described a series of N-heterocyclic carbenes (NHC) which form SAMs on gold. As the carbene is attached to the surface via a metal-carbon bond, the problem of sulfidization may be overcome. Here, I describe the synthesis of a peptide for the application of heavy metal detection with …
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N-Heterocyclic Carbenes of the Late Transition Metals: A Computational and Structural Database Study
A computational chemistry analysis combined with a crystallographic database study of the bonding in late transition metal N-heterocyclic carbene (NHC) complexes is reported. The results illustrate a metal-carbon bond for these complexes, approximately 4% shorter than that of a M-C single bond …
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Dianionic Janus-Type N-Heterocyclic Carbenes and their Zwitterionic Gold and Silver Metal Complexes
… neutral multitopic nonchelating N-heterocyclic carbenes (NHCs), limited progress has been made in the development of anionic counterparts. This thesis describes the synthesis and characterization of two new dianionic bis(maloNHC). The corresponding thiones were generated by the reaction of the …
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Molecular-level study of N-heterocyclic carbenes: Binding modes and self-assembly on Au(111)
… gold-standard for thirty years, N-heterocyclic carbenes (NHCs) have recently been used to create SAMs that are more thermally and chemically stable. For example, NHCs based on diisopropyl benzimidazolylidene (NHCiPr) have been integrated into biosensors. The field of NHC-based material science …
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Development of N-Heterocyclic Carbenes as Organic Catalysts and Efficient Ligands in Palladium Mediated Transformations
N-Heterocyclic carbenes (NHCs) have emerged as appropriate replacements for phosphines in transition metal catalyzed cross-coupling chemistry. The advantages of NHCs over phosphines include ease of handling, minimal toxicity, stability and powerful electron donating properties. Improvement of …
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Preparation of Novel Carbenes and their Catalytic Application to the Cross-Benzoin, Aza-Benzoin and Stetter Reactions
N-Heterocyclic carbenes (NHCs) derived from bicyclic triazolium salts possessing a fused 6 membered ring were found to induce chemoselectivity in the cross-benzoin between aromatic and aliphatic aldehydes. Use of these catalysts gave rise to predominantly one cross-benzoin product which could be …
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Toward the Synthesis of Trianionic Cerberus-Type N-Heterocyclic Carbenes and their Zwitterionic Gold and Silver Complexes
… neutral multitopic nonchelating N-heterocyclic carbenes (NHCs), limited progress has been made in the development of their anionic counterparts. This thesis describes the synthesis and characterization of a novel anionic tris(maloNHC) and its corresponding transition metal complexes. The free …
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Study of Bis-Imidazol-2-Ylidines as Ligands for Transition Metal Catalyzed Coupling Reactions
Two bis-imidazol-2-ylidine N-heterocyclic carbenes have been employed as ancillary ligands in an attempt to illustrate their utility in the palladium-mediated preparation of aryl ethers from aryl halides. Ullman-type homo-coupling of the aryl halides persistently occurred instead of ether …
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Robust Nickel Catalysts Supported By Biaryl-Bridged Pyridyl-N-Heterocyclic Carbenes For Carbon Dioxide Reduction To Value-Added Products
Carbon dioxide is a greenhouse gas, but also represents a readily accessible C1 feedstock for conversion to solar fuels and value-added chemicals. However, CO2 is relatively inert and very negative voltages or strong chemical reductants are comfor its conversion. An additional challenge lies in …
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Surface chemistry of N-Heterocyclic carbenes and the self-assembly, structure, and properties of polymer metal-organic cage gels
… as well as persistent and non-persistent carbenes. We synthesize from the reviewed reports a mechanistic understanding of this chemistry and outline the road ahead in this field. Chapter 2. Addressable Carbene Anchors for Gold Surfaces New strategies to access functional monolayers could …
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Picosecond studies of free radical reactions in solution
… resonance (EPR) spectroscopy shows that these carbenes are ground-state triplets. These carbenes react with methanol to form 9-methoxy ethers. The absence of a heavy atom effect in this reaction suggests that intersystem crossing is not involved in the rate-determining step, and that diaryl …
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Synthesis of Electron Deficient N-heterocyclic-carbenes and Activity of Imidazol-2-imine Thioureate Ligand on Group 10 Transition Metals
Previous work in the Lavoie group has resulted in the synthesis of new imidazol-2-imine ligands that have low activity towards ethylene polymerization due to their electron rich nature. In an attempt to alleviate this an electron poor naphthalene-1,4-dione-IMes imidazol-2-imine ligand (L) was …
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