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Showing 1 to 20 of 24 for “"dirhodium"”.
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Alkylidene Dirhodium Chemistry
… complexes have been prepared from unsaturated dirhodium complexes and diazo compounds. Several aspects of the reactivity of the alkylidene group in these and related complexes have been examined.
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Spectroscopic and synthetic studies relating to a dirhodium hydroformylation catalyst
… identify the catalytically inactive mono- and dirhodium complexes formed upon fragmentation of the catalyst under hydroformylation conditions. Various in situ NMR methods such as 1D <sup>1</sup>H and <sup>31</sup>P, and 2D COSY, HMBC, and HMQC were employed and indicated the formation of the …
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Photochemical and time-resolved spectroscopic studies of dirhodium hydrogen-generating species
Photochemical and time-resolved spectroscopic studies of di- and mono-rhodium inorganic complexes were undertaken to elucidate the mechanism of photocatalytic hydrogen generation from hydrohalic acid solutions ...
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Heteroleptic dirhodium (II,II) complexes: synthesis, spectroscopy and applications in hydroformylation and hydroaminomethylation catalytic reactions
… of a series of bis-substituted heteroleptic dirhodium(II,II) complexes containing bridging acetate and chelating bipyridyl ligands is herein described. The protons at the 4- and 4'- positions of the bipyridyl ligands on the model complex 1 were substituted by either the electron withdrawing …
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Synthesis and characterization of dirhodium(II) formamidinyl complexes: preliminary studies as catalyst precursors for the allylic oxidation of cyclohexene
A series of symmetrical substituted formamidine-type ligands, (L1, L2 and L3) were synthesized via a solvent-free reaction, in which ethanol is produced as by-product. The ligands were characterized as to their spectroscopic and solid-state properties via FT-IR, UV-Vis and NMR spectroscopies …
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Dirhodium(II,II) paddlewheel complexes conjugated to a polypyridyl tris-amine scaffold: synthesis and application as asdjncaslpre-catalysts in the hydroformylation of 1-octene
… increasing the activity through multinuclearity. Dirhodium(II,II) complexes contain two rhodium atoms, a metal-metal bond and an oxidation state of 4+ over the bimetallic core, resulting in each rhodium atom having an oxidation state of 2+. The electronic and steric influences can be altered by …
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Late transition metal bimetallics for photocatalytic hydrogen production, M-X and C-H bond activation
… acid solution using a two-electron mixed valence dirhodium complex. Studies aimed at understanding and improving the photochemical quantum efficiency for challenging M-X (X = CI, Br-) bond photoactivations were undertaken by incorporating gold into a heterobimetallic rhodium-gold construct. …
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Design and use of novel metal catalysts in organic synthesis
… focuses on the design and synthesis of novel dirhodium carboxylate catalysts, and their precursor ligands, for use as enantioselective catalysts in transformations of α-diazocarbonyl compounds. Chapter One focuses on the literature background over the past thirty years in transition …
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Fluorescence-based detection methodologies for nitric oxide using transition metal scaffolds
… as Potential Nitric Oxide Sensors. Chapter 4. Dirhodium Tetracarboxylate Scaffolds as Reversible Fluorescence- Based Nitric Oxide Sensors.
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Synthesis, Structure, and Catalytic Activity of Bimetallic Rhodium Complexes in the Hydroformylation and Allylic Oxidation of Alkenes
… same ligands were also reacted with either the dirhodium trifluorotetraacetate [Rh2(TfOAc)4] or the traditional acetate [Rh2(OAc)4] dimers. Thes reactions yield a series of diphenylformamidinato-Rh(II) homoleptic bimetallic complexes C5 – C7 of the type [Rh2(R-dpf)4] (where R = H, CH3 or F) as …
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Rhodium(II)-Stabilized Vinylcarbenes: Synthetic Applications in Ylide, Cyclopropanation, and C-H Insertion Reactions
… Rh2(S,R-MenthAZ)4. The azetidinate ligated dirhodium catalysts were the only dirhodium catalysts surveyed which provided enantioselectivities >40% ee in either intermolecular C-H insertion or cyclopropanation reactions.
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Halogen-elimination photochemistry and oxygen-activation chemistry of late transition-metal complexes
… A new class of two-electron mixedvalent dirhodium and diiridium complexes is described. Featuring a coordinatively unsaturated M0 center, these complexes display an expansive reactivity with numerous small-molecule substrates. A dirhodium hydride complex, prepared by HCl addition to the …
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Computational Studies on Bimetallic Catalysis and X-ray Absorption Spectroscopy
… water/acetone systems and results in dicationic dirhodium complexes and monocationic dirhodium complexes respectively. DFT studies were used to determine the active catalyst and possible intermediates. Computational studies support the mechanism proposed by Prof. Stanley for hydrofomylation in …
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The Application and Evolution of Chiral Ion-Paired Rhodium(II,II) Tetracarboxylate Catalysts for Enantioselective Nitrene Transfer
… transfer chemistry employing chiral ion-paired dirhodium catalysts. The initial development of this catalyst family was reported previously by the Phipps group and their design is based on a strategy for the combination of transition metal complexes and cinchona alkaloid-derived chiral cations. …
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Investigations of Catalysts Which Utilise Non-Covalent Interactions to Control Enantioselectivity in Rhodium-Catalysed Amination of C(sp3)–H Bonds
… amination was attempted, wherein the ion-paired dirhodium(II) catalyst displayed much higher reactivity relative to Du Bois’ Rh2(esp)2. Interesting effects on regioselectivity were also observed, but results here were ultimately uninspiring. The final section of this thesis sought to construct a …
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Two-electron mixed-valence complexes small molecule activation and photocatalytic hydrogen production
… induce disproportionation of valence-symmetric dirhodium cores. Application of this knowledge to iridium provided the first example of a two-electron mixed-valence complex for this metal, Ir20,II(tfepma)3C12. X-ray diffraction studies reveal a coordination environment with two bridging tfepma …
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Ligand field considerations for the reactivity of high valent metal-oxo complexes and of bimetallic HX splitting photocatalysts
… the reactivity. Regarding HX splitting, a new dirhodium diphosphazane structure is evaluated for photocatalytic HX splitting behavior. The complex photoreduces protons but degrades quickly. Rational ligand modifications afford an indefinitely stable proton reduction photocatalyst. Upon proton …
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Two approaches to the design and synthesis of bimetallic complexes
<p>Dirhodium complexes have been known for their catalytic reactivities toward C-H bond activation for nearly two decades. However, both experimental and theoretical studies have not given a clear explanation on the roles of each metal in the reactivities, largely due to the limited number of …
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Development of Ion Pairing Strategies that Utilise Cations to Control Selectivity in Transition Metal-Catalysed Functionalisation of C–H Bonds
… through ion pairing to a negatively charged dirhodium complex. This thesis highlights the generality of ion pairing strategies towards addressing selectivity challenges in transition metal-catalysed functionalisations of C–H bonds. It is hoped that the results presented herein will stimulate …
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