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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/CN 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 CH bond of bridging methylene group, was found to react with PhINTs to result in the formation of a new CN bond and cleavage of one existing NC(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 CH insertion of a Ru(IV)-imido/nitrene intermediate and was found to undergo the observed CN bond cleavage. Such type of CN 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
A small ringed macrocyclic tetracarbene ligand was developed due to the inherent ability of N-heterocyclic carbenes (NHCs) to stabilize high oxidation states of transition metals. This new strong donor ligand was prepared by first synthesizing an 18-atom ringed macrocyclic tetraimidazolium ligand precursor. The tetraimidazolium can be prepared by a two-step procedure. This ligand precursor was deprotonated to prepare a monomeric platinum tetracarbene complex. A new iron macrocyclic tetra-carbene complex was synthesized by an in situ strong base deprotonation strategy of the ligand precursor. The iron tetracarbene complex was found to catalyze the aziridination of a wide array of functionalized aryl azides and a variety of substituted aliphatic alkenes, including tetra-substituted. The aziridination intermediate was probed by mass spectrometry and found to likely be and iron(IV) imido. Further investigation of this intermediate discovered that the an iron(IV) tetrazene forms when excess aryl azide was added, probably by a 1,3-cycloaddition of an additional equivalent of azide to an imido. Utilizing single crystal X-ray diffraction, NMR spectroscopy, and Mossbauer spectroscopy the metal center was formally assigned as a low spin (S = 0) iron(IV). Additional reactivity studies indicates this tetrazene is capable of performing aziridination and therefore is an additional reaction pathway in the catalytic cycle. A large disadvantage of the aforementioned iron tetracarbene catalyst is poor yield. To overcome low yields and to prepare several transition metal tetracarbene complexes, a dimeric macrocyclic tetracarbene silver complex was synthesized. This complex was shown to successfully extend transmetallation of polydentate NHCs beyond bidentate NHCs. The silver complex was utilized in the preparation of a variety of mononuclear tetracarbene complexes ranging from early first row to late third row transition metals in moderate to high. In an attempt to move toward improving solubility of the tetracarbene catalysts, a second generation variant with two borate moieties in the ligand backbone was utilized. With this dianionic 18-atom macrocyclic tetracarbene ligand, the first tetracarbene complexes of Group 13 and 14 metals were synthesized. The tin, indium, and aluminium tetracarbene complexes are structurally analogous to their catalytically active porphyrin or salen analogues.
This first handbook to focus solely on the application of N-heterocyclic carbenes in synthesis covers metathesis, organocatalysis, oxidation and asymmetric reactions, along with experimental procedures. Written by leading international experts this is a valuable and practical source for every organic chemist.
Gerard van Koten: The Mono-anionic ECE-Pincer Ligand - a Versatile Privileged Ligand Platform: General Considerations.- Elena Poverenov, David Milstein: Non-Innocent Behavior of PCP and PCN Pincer Ligands of Late Metal Complexes.- Dean M. Roddick: Tuning of PCP Pincer Ligand Electronic and Steric Properties.- Gemma R. Freeman, J. A. Gareth Williams: Metal Complexes of Pincer Ligands: Excited States, Photochemistry, and Luminescence.- Davit Zargarian, Annie Castonguay, Denis M. Spasyuk: ECE-Type Pincer Complexes of Nickel.- Roman Jambor and Libor Dostál: The Chemistry of Pincer Complexes of 13 - 15 Main Group Elements.- Kálmán J. Szabo: Pincer Complexes as Catalysts in Organic Chemistry.- Jun-ichi Ito and Hisao Nishiyama: Optically Active Bis(oxazolinyl)phenyl Metal Complexes as Multi-potent Catalysts.- Anthony St. John, Karen I. Goldberg, and D. Michael Heinekey: Pincer Complexes as Catalysts for Amine Borane Dehydrogenation.- Dmitri Gelman and Ronit Romm: PC(sp3)P Transition Metal Pincer Complexes: Properties and Catalytic Applications.- Jennifer Hawk and Steve Craig: Physical Applications of Pincer Complexes.
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
Pincer complexes are formed by the binding of a chemical structure to a metal atom with at least one carbon-metal bond. Usually the metal atom has three bonds to a chemical backbone, enclosing the atom like a pincer. The resulting structure protects the metal atom and gives it unique properties.The last decade has witnessed the continuous growth in the development of pincer complexes. These species have passed from being curiosity compounds to chemical chameleons able to perform a wide variety of applications. Their unique metal bound structures provide some of the most active catalysts yet known for organic transformations involving the activation of bonds. The Chemistry of Pincer Compounds details use of pincer compounds including homogeneous catalysis, enantioselective organic transformations, the activation of strong bonds, the biological importance of pincer compounds as potential therapeutic or pharmaceutical agents, dendrimeric and supported materials. * Describes the chemistry and applications of this important class of organometallic and coordination compounds* Covers the areas in which pincer complexes have had an impact* Includes information on more recent and interesting pincer compounds not just those that are well-known
Summarizing the emerging field of N-heterocyclic carbenes used in organocatalysis, this is an excellent overview of the synthesis and applications of NHCs focusing on carbon-carbon and carbon-heteroatom bond formation. Alongside comprehensive coverage of the synthesis, characteristics and applications, this handbook and ready reference also includes chapters on NHCs for polymerization reactions and natural product synthesis.