Synthesis of Ferrocene-based Ligands and Their Applications in Redox-switchable Catalysis for Selective Hydroamination Reactions PDF Download

Author: Brian Raymond Lydon
Publisher:
ISBN:
Category :
Languages : en
Pages : 67

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Book Description
This thesis contains results from three different projects. The first project focused on the synthesis of monoanionic ferrocene-based N, P ligands. 1-(tert-butyldimethylsilyl)amino-1'-diphenylphosphinoferrocene (fc(TBSNH)(PPh2)) was successfully synthesized and characterized by 1H, 31P, 13C NMR spectroscopy, and elemental analysis. Unfortunately, coordination to group 3 metal complexes was unsuccessful. The second project focused on the synthesis of redox-active ferrocene-based ligands and their applications in selective intramolecular hydroamination. Redox-active ligands can be used as a reversible trigger to control catalytic reactivity. Preliminary results observed by 1H NMR spectroscopy suggest that [1,1'-ferrocenedi(thio(3,5-di-tert-butyl-2-phenoxide)]Zr dibenzyl ((thiolfan2)ZrBn2) shows selectivity between primary and secondary alkeneamines depending on the oxidation state of the iron center. The final project was a computational study using density functional theory (DFT) to understand recent experimental findings involving ferrocene-functionalized biodegradable polymers. Gibbs free energy for six cyclic carbonate monomers and three [delta]-valerolactone monomers was calculated. Computational results correlated strongly with experimental data in that [delta]-valerolactones, which could not be polymerized, had a higher Gibbs free energy than cyclic carbonates, which could be polymerized.

Author: Yi Shen
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Developing methodologies to synthesize high-value products efficiently from simple substrates with control over the reactivity and selectivity is highly favored by the chemical industry. Employing assisted tandem catalysis, where serial reactions can be carried out in one pot, to achieve streamlined complex syntheses significantly reduces the number of steps and waste. Harnessing spatial and temporal control in catalysis enables approaches toward one-pot transformations and allows the integration of several catalytic processes. Ferrocene-based ligand-supported metal complexes represent a promising class of catalysts that can incorporate redox control over catalytic processes. We have developed a redox-controlled selective hydroamination reaction catalyzed by (thiolfan*)Zr(NEt2)2 (thiolfan*= 1, 1'-bis (2,4-di-tert-butyl-6-thiophenoxy)ferrocene). In situ switching of the catalyst's state during the reaction enables selectivity toward different substrates (Chapter 2).Incorporating the greenhouse gas CO2 into N-carboxyanhydrides (NCAs) followed by subsequent NCA utilization illustrates the possibility of integrating two synthetic steps in one vessel to afford a valuable material with possible CO2 recycling. To demonstrate the immense potential of integrating multi-step transformations in one pot, we developed a set of sustainable conditions for NCA synthesis (Chapter 3). Moreover, several metal catalysts supported by ferrocene-based ligands were found to catalyze NCA polymerization in the presence of a co-catalyst. To establish an integrated system composed of two incompatible processes, we aimed to compartmentalize the active reagents for each step. The structure of the ferrocene-based pro-ligand was modified for surface anchoring. Our efforts toward immobilizing ferrocene-supported metal catalysts onto conductive surfaces pave the way of achieving spatiotemporal control over the processes of NCA synthesis and polymerization (Chapter 4). In addition to the redox-switchable characteristic, ferrocene-based compounds provide a unique platform to support lanthanides and engender distinctive optical properties to them. We synthesized and characterized a series of ytterbium complexes displaying an ultra-narrow absorption in the ultraviolet-visible (UV-Vis) region. The extraordinarily narrow linewidth observed for (thiolfan)YbCl(THF) (thiolfan = 1,1'-bis(2,4-di-tert-butyl-6-thiomethylenephenoxy)ferrocene) allows us to investigate its applications toward magnetic field and liquid cell quantum sensing (Chapter 5).

Author: Li-Xin Dai
Publisher: John Wiley & Sons
ISBN: 3527322809
Category : Science
Languages : en
Pages : 433

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Book Description
This book meets the long-felt need for a reference on ferrocenes with the focus on catalysis. It provides a thorough overview of the synthesis and characterization of different types of chiral ferrocene ligands, their application to various catalytic asymmetric reactions, and versatile chiral materials as well as drug intermediates synthesized from them. Written by the "who's who" of ferrocene catalysis, this is a guide to the design of new ferrocene ligands and synthesis of chiral synthetic intermediates, and will thus be useful for organic, catalytic and synthetic chemists working in academia, industrial research or process development.

Author: Petr Stepnicka
Publisher: John Wiley & Sons
ISBN: 9780470985656
Category : Science
Languages : en
Pages : 670

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Book Description
Ferrocene—the prototypical metallocene—is a fascinating molecule. Even though it was first discovered over fifty years ago, research into ferrocene-containing compounds continues apace, largely stimulated by their successful applications in catalysis, materials science and bioorganometallic chemistry. Ferrocene derivatives are now recognised as useful starting materials for the preparation of new organometallic complexes and functional materials, efficient catalyst components, as well as redox-active modifiers to biomolecules. Ferrocenes: Ligands, Materials and Biomolecules provides the reader with a background overview and describes recent advances in the development and application of ferrocene compounds, including: synthesis and catalytic utilisation of chiral and non-chiral ferrocene ligands ferrocene-based sensors electrooptical materials ferrocene polymers liquid-crystalline materials crystal engineering with ferrocene compounds the bioorganometallic chemistry of ferrocene Ferrocenes: Ligands, Materials and Biomolecules is an essential guide for anyone working in the fields of organometallic synthesis and catalysis, materials science and bioorganometallic chemistry.

Author: Li Wang
Publisher: Springer
ISBN: 9811060622
Category : Technology & Engineering
Languages : en
Pages : 112

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Book Description
After an introduction to their fundamentals and history, this book systematically reviews ferrocene-based compounds, polymers and hydrogels. It explains in detail the synthetic methods for and properties of each ferrocene-based compound, polymer and hydrogel, and also extensively discusses their applications, including electrochemistry, catalysis and sensors. An outlook chapter on remaining challenges and future perspectives rounds out the coverage. Providing a wealth of valuable information on ferrocene-related studies, the book appeals to researchers, professionals and graduate students working in the fields of organic and polymer chemistry, as well as materials science.

Author: Antonio Togni
Publisher: John Wiley & Sons
ISBN: 352761558X
Category : Science
Languages : en
Pages : 560

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Book Description
With applications ranging from asymmetric catalysis to magnetic materials, ferrocene is one of the most versatile building blocks in synthesis. This book captures the multidisciplinary nature of ferrocene research, including topics such as ferrocene-containing polymers, ferrocene-containing thermotropic liquid crystals, chiral ferrocene derivatives, and ferrocene-containing charge-transfer materials. In addition, the reader will find * valuable information for planning syntheses * over 70 tables, making relevant data available at a glance * carefully selected references, providing an easy access to the primary literature Up-to-date, and written by leading international experts in the field, among them R. Deschenaux, C. D. Hall, Y. Butsugan, and R. Herrmann, this book is a welcome source of in-depth information for graduate students and professionals in organic, organometallic, and polymer chemistry, as well as in materials science.

Author: Tate Reuter
Publisher:
ISBN:
Category :
Languages : en
Pages : 66

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Book Description
Ferrocene-chelating heteroscorpionate compounds based on [fc(PPh2)(BH[(3-R-5-R'-1-H)2pz]2)] (fc = 1,1'-ferrocenediyl, pz = pyrazole) are studied and characterized for their role in the synthesis of block copolymers. The ferrocene scaffold is part of a heteroscorpionate ligand that supports late transition metals. A zinc complex, [fc(PPh2)(BH[(3,5-Me-1H)2pz]2)]Zn( -OCH2Ph), was synthesized previously and shown to exist in a dimeric state. Herein, the substituents on the pyrazole fragments of the scorpionate are replaced with bulkier groups to force the formation of a monomeric compound in order to arrive at a redox switchable catalyst.

Author: Evelyn Louise Rosen
Publisher:
ISBN:
Category :
Languages : en
Pages : 286

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Book Description
With the ever expanding utility of transition metal catalysis, there has been a thrust both to develop catalysts with unique selectivites or activites, and to understand the factors which govern these characteristics at both a fundamental and practical level. Olefin metathesis has become an essential reaction for the synthesis of small molecules in addition to polymeric materials. We have pursued two distinct ligand classes based on diaminocarbenes with novel architectures to address specific limitations within this useful class of reactions: 1) limited access to polymeric materials with controlled microstructures and 2) poor stereoselectivity in Ru-catalyzed cross-metathesis (CM) reactions. Numerous phosphines and N-heterocyclic carbenes (NHCs) have been used as ligands for Ru metathesis catalysts, and the resulting activity is very sensitive to their steric and electronic nature. We envisioned that we could take advantage of this dependence by developing a catalyst with tunable ligand donicity. Redox-switchable ligands can lead to catalysts whose selectivity and/or activity are dependent upon the ligand oxidation state. Towards this purpose, we have developed a ligand which incorporates a 1,1'-disubstituted ferrocene moiety into the backbone of a diaminocarbene (FcDAC). Upon ligation of FcDAC to various transition metals, we were able to use cyclic voltammetry and a spectroelectrochemical FT-IR experiment to show electronic communication between FcDAC and the coordinated metal. We then pursued Ru metathesis catalysts incorporating these ligands. The ring-opening metathesis polymerization of 1,5-cyclooctadiene was studied using [(FcDAC)(PPh3)Cl2Ru=(3-phenylindenylid-2-ene)] as the catalyst. Chemical redox reactions were used to establish the ability of FcDAC to impart redox-tunable properties to Ru metathesis catalysts. A new ligand class pioneered in our group, N-aryl, N-alkyl acyclic diaminocarbenes (ADCs), was also studied in various Ru metathesis catalysts. To our delight, these catalysts showed lower E : Z ratios than analogous NHC ligands in two representative CM reactions. We also investigated the conformational diversity of these differentially substituted ADCs given their ability to rotate about their C-N bonds, in particular, to determine how this might influence their donicity. Complexes of the type [(ADC)Ir(COD)Cl] and [(ADC)Ir(CO)2Cl] were studied, given the wealth of structural and spectral data available for analogous compounds incorporating related ligand classes. Different conformations resulted depending on the N-substituents and the nature of the metal complex. Interestingly, the electron donating ability of ADC ligands was found to depend on their conformation, as evidenced by FT-IR and cyclic voltammetry. This established a new avenue for tuning the donor properties of differentially substituted ADC ligands. The unique properties of these novel ligand classes were demonstrated in Ru metathesis catalysts. However, on a broader level, these ligands are expected to have utility in diverse catalytic applications.

Author: Uttam Das
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
The development of abundant and economical first-row transition metal-based catalysts is an appealing area of research for efficient and selective chemical transformations. In this context, iron complexes are highly desirable as they feature a range of accessible oxidation states allowing for transfer of one or two electrons to or from a substrate. Therefore, over the past two decades, many iron-based catalysts have been developed, extensively studied, and exploited for catalysis ranging from oxidation and reduction to C-C bond forming reactions. In homogeneous transition metal catalysis, the ligand plays a vital role in determining activity and selectivity of the above stated catalytic reactions. Some key features of ligands that support both stoichiometric and catalytic reactions of metal complexes include: 1) strong chelation ability to metals, 2) tunability of donor atoms, 3) strong field ligands such as phosphine, phosphite, CO, and hydride favoring low-spin complexes, 4) hemilability allowing substrate activation via reversible dissociation of one donor atom, and 5) redox-activity enabling donation or accepting of electrons, thus avoiding a change of metal oxidation state. To this end, bifunctional ligands containing the above described properties have emerged as important elements in chemical synthesis and in catalysis. Iron and other transition metal complexes containing multidentate bifunctional ligands have recently been shown to activate small molecules and catalyze a number of chemical transformations with activity and selectivity typical of more well-studied precious metals. The objective of this thesis is to further advance the field of bifunctional ligands by preparing new sterically svelte tridentate ligands with a mixture of hard nitrogen and soft sulfur donors and to investigate their iron chemistry. The overall goal is to then explore the utility of these iron complexes as potential bifunctional catalysts. Chapter 2 describes a one-step synthesis of a new SMeNHS ligand in excellent yield that undergoes ring-opening on treatment with Fe(OTf)2 affording a thiolate-bridged, trinuclear iron complex, [Fe3(μ2-SMeNS−)4](OTf)2. The structure, spectroscopic, magnetic, and computational studies of this iron complex are provided along with its solvent-dependent reactivity towards monodentate donor ligands that yields both dinuclear and mononuclear derivatives. Chapter 3 describes the formation of an electron-rich Fe(II) thiolate complex, [Fe(SMeNS)(PMe3)3](OTf) and its substitution reactivity with both mono- and bidentate donor ligands. On heating this complex, an oxidative thioether Caryl-S bond cleavage is observed, leading to a cationic Fe(III)-CNS thiolate analog. Reduction of this Fe(III) species with cobaltocene yielded a neutral Fe(II)-CNS thiolate complex. To investigate the bifunctional activity of these Fe(II) complexes, both Fe(II)-SNS and -CNS species were assessed as precatalysts for amine-borane dehydrogenation. Chapter 4 employs the SMeNHS ligand in formation of a neutral, imine-coupled Fe-N2S2 complex that serves as an efficient and selective aldehyde hydroboration catalyst using pinacolborane. A reaction profile kinetic analysis implicates the hemilability and redox-active properties of this complex. Chapter 5 introduces the new unsymmetrical amine ligand, SMeNHSMe, and details its iron chemistry with formation of a pseudooctahedral Fe(II) bis(amido) complex. The Mössbauer spectra, MCD study, and DFT calculations support formation of a minor five-coordinate isomer in solution due to the hemilability of the six-membered ring thioether group. Reactivity studies of this Fe(II) species with a variety of donor ligands confirmed this lability and protonation at nitrogen yielded a cationic Fe(II) amine-amido complex. Reaction of the latter with the tridentate phosphine, triphos, gave a 16e-, low-spin, square-pyramidal Fe(II) complex that proved to be a robust precatalyst that is more active for dehydrogenation of dimethylamine-borane vs. ammonia-borane. Formation of a monohydride catalyst resting state under these reaction conditions is suggestive of a bifunctional activation pathway. Finally, Chapter 6 concludes the outcomes of the iron chemistry of hemilabile SNS ligands and discusses future directions and opportunities to extend these ligand systems to other transition metals. The knowledge gained by the stoichiometric and catalytic reactivity of iron-SNS complexes presented herein contributes to our understanding of bifunctional catalysis. With the increasing demand for base metal catalysts in chemical industry for efficient and selective synthesis of value-added chemicals, iron SNS complexes could offer economical, active, and selective catalyst precursors.

Author: Alan Martin Allgeier
Publisher:
ISBN:
Category :
Languages : en
Pages :

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A new redox-active HE(II) sequestering ligand, ($\eta\sp5$-C$\rm\sb5H\sb4SCH\sb2CH\sb2SH)\sb2$Fe, 5, has been synthesized and characterized. Ligand 5 undergoes a reaction with Hg(ClO$\sb4)\sb2$, which has been detected by $\sp1$H NMR spectroscopy and cyclic voltammetry in DMSO.