High- and Low-Valent tris-N-Heterocyclic Carbene Iron Complexes

High- and Low-Valent tris-N-Heterocyclic Carbene Iron Complexes
Author: Carola S. Vogel
Publisher: Springer Science & Business Media
Total Pages: 145
Release: 2012-02-03
Genre: Science
ISBN: 3642272533

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Carola Vogel’s PhD thesis focuses on the synthesis, and structural and spectroscopic characterization of the first high valent iron nitride complexes. In her interdisciplinary and collaborative research Carola also describes the reactivity studies of a unique iron (V) nitride complex with water. These studies show that quantitative yields of ammonia are given at ambient conditions. High valent iron nitride and oxo species have been proposed as key intermediates in many bio-catalytic transformations, but until now these species have proven exceedingly challenging to isolate and study. Iron complexes in high oxidation states can thus serve as models for iron-containing enzymes to help us understand biological systems or aid our development of more efficient industrial catalysts.

N-Heterocyclic Carbenes in Synthesis

N-Heterocyclic Carbenes in Synthesis
Author: Steven P. Nolan
Publisher: John Wiley & Sons
Total Pages: 319
Release: 2006-12-13
Genre: Science
ISBN: 3527609407

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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.

N-Heterocyclic Carbenes in Transition Metal Catalysis

N-Heterocyclic Carbenes in Transition Metal Catalysis
Author: Frank Glorius
Publisher: Springer
Total Pages: 240
Release: 2007-02-05
Genre: Science
ISBN: 3540369309

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In this book leading experts have surveyed major areas of application of NHC metal complexes in catalysis. The authors have placed a special focus on nickel- and palladium-catalyzed reactions, on applications in metathesis reactions, on oxidation reactions and on the use of chiral NHC-based catalysts. This compilation is rounded out by an introductory chapter and a chapter dealing with synthetic routes to NHC metal complexes.

Investigation of Iron-N-Heterocyclic Carbene Complexes for Photocatalytic Applications

Investigation of Iron-N-Heterocyclic Carbene Complexes for Photocatalytic Applications
Author: Aleksandra Ilić
Publisher:
Total Pages: 0
Release: 2024
Genre:
ISBN: 9789180960403

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Humanity's ever-growing energy demands require the implementation of more sustainable ways to harvest and store energy. At the same time, the reduction of greenhouse gas emission and thus global warming remains of paramount importance. To this end, solar energy harvesting presents an attractive route towards satisfying these requirements--be that by conversion to thermal energy, electricity or to chemical energy. Molecular systems based on iron could prove particularly interesting in this area, due to their advantageous properties such as appreciable visible light-absorption as well as the high availability and low cost of iron. As of yet, they have not been extensively studied though, which can be attributed to the inherently poor photophysical and -chemical properties associated with these systems. However, well thought-out structural design can be used to combat said issues. The ligand motif used in Fe-N-heterocyclic carbene (NHC) complexes aids in mitigating the formerly mentioned unfavourable properties, allowing for bimolecular quenching with electron donors and acceptors to occur, which is crucial for photocatalysis. In this thesis, the application of hexa-NHC complexes based on Earth-abundant iron as light-harvesters for solar-to-chemical energy conversion is demonstrated. The utility of Fe(III)-NHC complexes for sensitisation of artificial photosynthesis reactions as well as their performance as photoredox catalysts in organic transformations has been studied and the underlying mechanisms have been investigated, giving insight into the prospects and limitations associated with these systems. For the hydrogen evolution and aminomethylation reactions investigated here, conventional single-photon mechanisms were observed. Meanwhile, in the case of the atom transfer radical addition reactions, sequential photon absorption of two different oxidation states of the catalyst within the same catalytic turnover was shown to be operative. Furthermore, a study featuring the Fe(II)-congener of an Fe(III)-NHC complex with demonstrated photocatalytic activity revealed a less than favourable excited state lifetime compared to the Fe(III)-parent complex, showcasing that the preparation of Fe(II)-NHC complexes with synthetically useful photophysical and chemical properties is not necessarily facile. Early investigations of a photocatalytic reaction driven by heterogenisation of Fe(III)-NHC complexes are also shown. There the goal was to improve upon the sustainability of these catalysts by facilitating their recyclability. This thesis thus showcases the potential of Fe-NHC complexes for photocatalytic applications, whilst also revealing their shortcomings.

N-Heterocyclic Carbenes

N-Heterocyclic Carbenes
Author: Silvia Diez-Gonzalez
Publisher: Royal Society of Chemistry
Total Pages: 636
Release: 2016-11-08
Genre: Science
ISBN: 1782624236

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In less than 20 years N-heterocyclic carbenes (NHCs) have become well-established ancillary ligands for the preparation of transition metal-based catalysts. This is mainly due to the fact that NHCs tend to bind strongly to metal centres, avoiding the need of excess ligand in catalytic reactions. Also, NHC‒metal complexes are often insensitive to air and moisture, and have proven remarkably resistant to oxidation. This book showcases the wide variety of applications of NHCs in different chemistry fields beyond being simple phosphine mimics. This second edition has been updated throughout, and now includes a new chapter on NHC‒main group element complexes. It covers the synthesis of NHC ligands and their corresponding metal complexes, as well as their bonding and stereoelectronic properties and applications in catalysis. This is complemented by related topics such as organocatalysis and biologically active complexes. Written for organic and inorganic chemists, this book is ideal for postgraduates, researchers and industrialists.

Science of Synthesis: N-Heterocyclic Carbenes in Catalytic Organic Synthesis Vol. 2

Science of Synthesis: N-Heterocyclic Carbenes in Catalytic Organic Synthesis Vol. 2
Author: Steven Nolan
Publisher: Thieme
Total Pages: 816
Release: 2017-06-14
Genre: Science
ISBN: 3132414034

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The field of N-heterocyclic carbenes, whether in transition-metal catalysis or organocatalysis, is rapidly evolving towards applications, but is also still very active on the catalyst development front. Significant advances have been made over the past two decades and the development of these reactions has dramatically improved the efficiency of organic synthesis. N-Heterocyclic carbene based catalysts are now widely applied in the area of synthesis of both natural products and therapeutic agents. "Science of Synthesis: N-Heterocyclic Carbenes in Catalytic Organic Synthesis" presents the most commonly used and significant metal- or non-metal-catalyzed reactions for modern organic synthesis. The basic principles and current state-of-the-art of the methods are covered. Scope, limitations, and mechanism of these reactions are discussed and key experimental procedures are included. Typical examples of target synthesis are often provided to show the utility and inspire further applications.

N-Heterocyclic Carbenes

N-Heterocyclic Carbenes
Author: Steven P. Nolan
Publisher: John Wiley & Sons
Total Pages: 690
Release: 2014-07-07
Genre: Science
ISBN: 3527671242

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This comprehensive reference and handbook covers in depth all major aspects of the use of N-heterocyclic carbene-complexes in organic synthesis: from the theoretical background to characterization, and from cross-coupling reactions to olefin metathesis. Edited by a leader and experienced scientist in the field of homogeneous catalysis and use of NHCs, this is an essential tool for every academic and industrial synthetic chemist.

N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis

N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis
Author: Catherine S.J. Cazin
Publisher: Springer Science & Business Media
Total Pages: 348
Release: 2010-10-04
Genre: Science
ISBN: 9048128668

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N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis features all catalytic reactions enabled by N-heterocyclic carbenes (NHCs), either directly as organocatalysts or as ligands for transition metal catalysts. An explosion in the use of NHCs has been reported in the literature during the past seven years making this comprehensive overview highly apropos. The book begins with an introductory overview of NHCs which could have been subtitled all you need to know about NHCs. The main body of the book is dedicated to applications of NHCs in catalysis. In addition to the success stories of NHCs in metathesis, NHCs in cross coupling and more recently NHCs in organocatalysis, all other less publicized areas are also covered. As the success of NHCs is generally attributed to their potential to stabilize metal centres, the inclusion of a chapter on the decomposition of NHC catalysts is pertinent. The book closes with a chapter describing the applications of NHCs in industrial processes, which is the first coverage of its kind, and brings a unique industrial context to this book. Included in this book: Historical aspects of NHCs Synthetic pathways to NHC precursors, free NHCs and complexes Methods of characterisation of NHCs and related complexes Electronic properties of NHCs Steric properties of NHCs and models for their description NHCs for metathesis and cross-coupling reactions NHCs as organocatalysts NHC Transition-Metal mediated oxidations, additions to multiple bonds, polymerisation and oligomerisation, cyclisations, direct arylations, reactions involving CO, C-F and C-H bond activation, ... Decomposition of NHC-containing catalysts Industrial applications involving NHC-containing catalysts N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis provides a fresh view of NHCs since most contributors are young emerging researchers in the field of homogeneous catalysis using NHCs. This group of contributors is complemented by highly established academic researchers and an industrialist. This book is comprehensive, from the basic features of NHCs to the latest advances, hence it is suitable for both the novice and the expert.

Chiral Iron Pyridine Complexes and Ruthenium Complexes with N-Heterocyclic Carbene and Macrocyclic (N, O) Donor Atom Ligands

Chiral Iron Pyridine Complexes and Ruthenium Complexes with N-Heterocyclic Carbene and Macrocyclic (N, O) Donor Atom Ligands
Author: Kar-Yee Lam
Publisher:
Total Pages:
Release: 2017-01-26
Genre:
ISBN: 9781361034422

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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