Late Transition Metal Complexes Containing Tridentate Pincer-type 1, 3-bis (o-diphenylphosphino) Phenyl)-N, N'-heterocyclic Phosphenium/carbene Ligands PDF Download
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Author: Baofei Pan
Publisher:
ISBN:
Category : Ligands
Languages : en
Pages : 175
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Author: Baofei Pan
Publisher:
ISBN:
Category : Ligands
Languages : en
Pages : 175
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Author: Wilson D. Bailey
Publisher:
ISBN:
Category : Alkenes
Languages : en
Pages : 181
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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.
Author: Susan Conde Guadano
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Category :
Languages : en
Pages :
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The new indenyl-functionalised NHC potassium salt, 1-[3-(4,7-dimethylindenylpropyl)]-3- (2,6-diisopropylphenyl)imidazol-2-ylidenepotassium, has been synthesised. Complexes of titanium, zirconium and chromium containing this ligand and the two carbon bridge analogue, 1-[2-(4,7-dimethylindenyl)ethyl]-3-(2,6-diisopropylphenyl)imidazol-2 ylidene potassium, have been synthesised and characterised by X-ray crystallographic techniques. The following complexes were tested as catalysts for the oligomerisation of ethylene in the presence of MAO: 3-(2,6-diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidene(tertbutylimido) titanium chloride, 3-(2,6-diisopropylphenyl)-1-[3-(4,7- dimethylindenyl)propyl]imidazol-2-ylidene(tert-butylimido)titanium chloride, 3-(2,6- diisopropylphenyl)-1-[3-(4,7-dimethylindenyl)propyl]imidazol-2-ylidenezirconium trichloride, 3-(2,6-diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]imidazol-2- ylidenezirconium trichloride, 3-(2,6-Diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]- imidazol-2-ylidenechromium dichloride, 3-(2,6-diisopropylphenyl)-1-[3-(4,7- (dimethylindenyl))propyl]imidazol-2-ylidene chromium dichloride, 3-(2,6-diisopropylphenyl)- 1-[3-(4,7-dimethylindenyl)propyl]-imidazol-2-ylidene chromium methyl chloride and 3-(2,6- diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidenevanadium dichloride. The following alkyl chromium complexes containing 1-[2-(4,7-dimethylindenyl)ethyl]-3-(2,6- diisopropylphenyl)imidazol-2 ylidene potassium have also been synthesised: 3-(2,6- diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidene chromium phenyl chloride and 3-(2,6-diisopropyl-phenyl)-1-[2-(4, 7-dimethylindenyl)ethyl]-imidazol-2-ylidene chromium dibenzyl. Chromium cations have been synthesised using as starting materials the chromium alkyl complexes. The Cr(II) complex 3-(2,6-diisopropyl-phenyl)-1-[2-(4, 7- dimethylindenyl)ethyl]-imidazol-2-ylidene chromium monochloride and a partially oxidised dimerised product were also isolated. 5-(2-chloroethyl)- 1, 2, 3, 4-tetramethylcyclopentadiene and 5-(3-chloropropyl) 1, 2, 3, 4-tetramethylcyclopentadiene were synthesised and isolated as geminal isomers for the first time. The trialkyl chromium complex, tribenzyl chromium tris(tetrahydrofuran) was synthesised and also it was used as starting material for the complexes di(benzyl)chromium bis(1, 3- diisopropylimidazol-2-ylindene) and tri(benzyl)chromium TACN. All complexes were characterised by X-ray crystallography. The imidazolium salt 3-(2.6-diisopropylphenyl)-1-[N, N-bis(2,6- diisopropylphenyl)acetamidyl] imidazolium chloride was synthesised and used as a precursor for the synthesis of amidinate-functionalised NHC zirconium and amidine-functionalised NHC silver complexes. Double deprotonation of 3-(2,6-diisopropylphenyl)-1-[N, N'-bis(2,6- diisopropylphenyl)acetamidyl] imidazolium chloride gave the amidinate-functionalised NHC ligand, 3-(2.6-diisopropylphenyl)-1-[2-N, N'bis(2,6 diisopropylphenylamidinate)ethyl]imidazol-2-ylidenepotassium. Titanium, zirconium and chromium complexes containing this ligand were synthesised and characterised by X-ray crystallographic techniques. Transmetallation of the amidine-functionalised NHC silver complex with [Rh(COD)Cl]2 and [Ir(COD)Cl]2 gave the corresponding species. Rh(amidinefunctionalised NHC)(COD)Cl reacted with Na(BAr)4 (Ar = 3,5-CF3C6H3) to give the cation Rh(amidine-functionalised NHC)(COD)]+[BAr4]-. These species were also characterised by X-ray diffraction techniques.
Author: Philip Edward Reedy
Publisher:
ISBN:
Category :
Languages : en
Pages : 614
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Author: Brian Christopher Gruver
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ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 148
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Author:
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Category :
Languages : en
Pages : 122
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Author: Michael David Mulvihill
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Category :
Languages : en
Pages :
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Author: Kar-Yee Lam
Publisher:
ISBN: 9781361034422
Category :
Languages : en
Pages :
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This dissertation, "Chiral Iron Pyridine Complexes and Ruthenium Complexes With N-heterocyclic Carbene and Macrocyclic (N, O) Donor Atom Ligands: Synthesis, Catalytic Activity and Biological Studies" by Kar-yee, Lam, 林嘉儀, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled CHIRAL IRON PYRIDINE COMPLEXES AND RUTHENIUM COMPLEXES WITH N-HETEROCYCLIC CARBENE AND MACROCYCLIC(N, O) DONOR ATOM LIGANDS: SYNTHESIS, CATALYTIC ACTIVITY AND BIOLOGICAL STUDIES Submitted by Lam Kar Yee For the degree of Doctor of Philosophy at The University of Hong Kong in April 2016 Transition metal complexes are widely applied as catalysts for organic transformation reactions such as the oxygen atom and nitrene transfer reactions and there is a growing interest to develop the medicinal applications of transition metal complexes. The studies of reactive metal-oxo and metal-nitrene intermediates are important in probing the underlying reaction mechanisms. This thesis is comprised of three main parts. In the first part, iron complexes with chiral pyridine ligands, such as 4′,6-disubstituted 2,2′ 6′,2″-terpyridine (NNN ) and 4′,6,6″-trisubstituted 2,2′ 6′,2″''-terpyridine (NNN ), were studied for their catalytic activities in asymmetric epoxidation, aziridination, amidation and sulfimidation reactions. The Fe-NNN complex catalyzed intermolecular nitrene transfer/CN bond formation reactions of styrenes with PhINTs in moderate product yields. For the asymmetric intramolecular amidation, the Fe-NNN complex can catalyze intramolecular C-N bond formation using PhI(OAc) as oxidant to form five- or six-membered ring products. The highest product yield obtained was 91 %. The complete conversion of para-substituted phenyl methyl sulfides to corresponding sulfimides was observed by using the Fe-NNN 1 2 complex as catalyst. Both the Fe-NNN and Fe-NNN complexes catalyzed asymmetric epoxidation of styrene using PhIO as oxidant at 0 C. The reaction intermediates of the nitrene/oxygen transfer reactions were studied by ESI-MS and high-valent iron-ligand multiple bonded species are proposed to be the reaction intermediates. In the second part, ruthenium pincer N-heterocyclic carbene (CNC) complexes were prepared and characterized by spectroscopic means and X-ray crystallography. II 2+ Complex [Ru (CNC)(bpy)(MeCN)], in which the CNC ligand adopts a fac-coordination mode and contains reactive CH bond of bridging methylene group, was found to react with PhINTs to result in the formation of a new CN bond and cleavage of one existing NC(methylene) bond of the CNC ligand, as revealed by X-ray crystal structure determination of the ruthenium complex product. The reaction 2+ of [Ru(CNC)(bpy)(MeCN)] with PhINTs was monitored by ESI-MS, UV-vis, and NMR spectroscopy; a paramagnetic Ru(III)-amido complex was isolated, which apparently resulted from intramolecular imido/nitrene CH insertion of a Ru(IV)-imido/nitrene intermediate and was found to undergo the observed CN bond cleavage. Such type of CN bond cleavage induced by metal-mediated imido/nitrene insertion is unprecedented in literature. The final part of this thesis is the study of the anti-angiogenic and anti-metastatic properties of the ruthenium complexes. Ruthenium complexes with different oxidation states (+2 and +3) and ligands (pincer NHC and macrocyclic (N, O) donor atom ligands) were examined for their cytotoxicity and anti-angiogenesis activity. III Among the complexes studied, [Ru (N O )Cl ]Cl (Ru-1) displays promising 2 2 2 inhibi
Author: Angela T. Slade
Publisher:
ISBN:
Category : Asymmetric synthesis
Languages : en
Pages : 408
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The objective of this thesis are two-fold. First to ascertain how phosphinite compounds behave when reacted with transition metal substrates. The second objective is to establish whether the resulting complexes were asymmetric catalysts for conversion of prochiral substrates to chiral products in high ee.
Author: Bradley George Anderson
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 376
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