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Synthesis Of Low Coordinate Transition Metal Bisalkoxide Complexes And Their Reactivity Toward Small Molecules
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Book Synopsis Synthesis of Low-coordinate Transition Metal Bis(alkoxide) Complexes and Their Reactivity Toward Small Molecules by : Maryam Yousif
Download or read book Synthesis of Low-coordinate Transition Metal Bis(alkoxide) Complexes and Their Reactivity Toward Small Molecules written by Maryam Yousif and published by . This book was released on 2017 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focused on the synthesis of new transition metal complexes in bis(alkoxide) ligand environments and the investigation of their reactivity in nitrene-group transfer catalysis and small molecule activation. Treatment of Cr(N(SiMe3)2)2(THF)2 with two equivalents of HOR (OR = OCtBu2Ph) led to the formation of the chromium(II) alkoxide dimer, Cr2(OR)4. Upon the reaction with bulky aryl and alkyl azides, Cr2(OR)4 led to the stable Cr(IV) mono(imido) complexes, Cr(OR)2(NR), featuring trigonal planar metal centers. In contrast, less bulky aryl azides led to the formation of chromium (VI) bis(imido) complexes Cr(OR)2(NR)2, independent of the amount of azide used. Chromium(IV) mono(imido) species Cr(OR)2(NR) is capable of nitrene transfer to isocyanides to form asymmetric carbodiimides (RNCNR'). When excess isocyanide is added to Cr(OR)2(NR), a new chromium(II) complex, Cr(OR)2(CNR2)4, was identified by X-ray crystallography. This tetrakis(isocyanide) chromium(II) complex is also capable of forming carbodiimide when azide is introduced. Efficient catalytic formation of carbodiimides was obtained using 2.5 mol% of Cr2(OR)4 for the mixtures of bulky organoazides and isocyanides; no catalytic reactivity was observed for the non-bulky aryl azides. DFT calculations suggest that trigonal CrIV(OR)2(NR) intermediate is the key species in the reaction mechanism as, due to it coordinative unsaturation, it allows isocyanide binding to the metal, which enables subsequent C-N bond formation. A bulkier alkoxide ligand HOR' (R = CtBu2(3,5-Ph2Ph)) was synthesized by lithium halogen exchange reaction. The protonolysis of the metal complexes, M(N(SiMe3)2(THF)x, with HOR' enabled an easy isolation of new bis(alkoxide) precursors M(OR')2(THF)2 (where M = Cr, Co, Fe) featuring cis-divacant octahedral geometry. The chemistry of the iron bis(alkoxide) compound Fe(OR')2(THF)2 with the variety of aryl azides was investigated.
Book Synopsis Transition Metals in the Synthesis of Complex Organic Molecules by : Louis S. Hegedus
Download or read book Transition Metals in the Synthesis of Complex Organic Molecules written by Louis S. Hegedus and published by University Science Books. This book was released on 1999 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: This second edition offers easy access to the field of organotransition metal chemistry. The book covers the basics of transition metal chemistry, giving a practical introduction to organotransition reaction mechanisms.
Book Synopsis Synthesis, Characterization and Reactivity Studies of Low-coordinate Late Transition Metal Complexes and the Preparation and Characterization of a Low-coordinate Samarium Complex by : Pei Zhao
Download or read book Synthesis, Characterization and Reactivity Studies of Low-coordinate Late Transition Metal Complexes and the Preparation and Characterization of a Low-coordinate Samarium Complex written by Pei Zhao and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the synthesis, characterization and reactivity study of terphenyl ligand stabilized bis([mu]-oxo) dimeric iron and cobalt complexes. The synthesis and characterization of low-coordinate cobalt alkyl and iron alkyl complexes are also described. In addition, it describes the preparation of the first monomeric homoleptic solvent-free bis(aryloxide) lanthanide complex. The solid state structures of new compounds were determined by single crystal X-ray crystallography. Magnetic properties of paramagnetic compounds were measured by superconducting quantum interference device (SQUID) or Evans' methods for solid state or solution phase, respectively. The new compounds were also characterized by UV-Visible spectroscopy. Furthermore, infrared spectroscopy, Mössbauer spectroscopy, electron paramagnetic resonance spectroscopy, mass spectrometry, cyclic voltammetry and elemental analysis were employed to characterize some of the compounds when applicable. In some cases, DFT calculations were applied to elucidate the bonding and energy levels of molecular orbitals in the complexes. In Chapter 2, The bis([mu]-oxo) dimeric complexes {Ar[superscript iPr8]OM([mu]-O)}2 (Ar [superscript iPr8] = -C6H-2,6-(C6H2-2,4,6-[superscript i]Pr3)2-3,5-[superscript i]Pr2; M = Fe or Co) were prepared by oxidation of the metal (I) half-sandwich complexes {Ar[superscript iPr8]M([eta]6-arene)} (arene = benzene or toluene; M = Fe or Co). The iron species {Ar[superscript iPr8]OFe([mu]-O)}2 was prepared by reacting {Ar[superscript iPr8]Fe([eta]6-benzene)} with N2O or O2 and the cobalt species {Ar[superscript iPr8]OCo([mu]-O)}2 was prepared by reacting {Ar[superscript iPr8]Co([eta]6-toluene)} with O2. Both {Ar[superscript iPr8]OFe([mu]-O)}2 and {Ar[superscript iPr8]OCo([mu]-O)}2 were characterized by X-ray crystallography, UV-vis spectroscopy, magnetic measurements and, in the case of the iron species, by Mössbauer spectroscopy. The solid-state structures of both compounds reveal unique M2([mu]-O)2 (M = Fe or Co) cores with formally three-coordinate metal ions. The Fe···Fe separation in {Ar[superscript iPr8]OFe([mu]-O)}2 bears a resemblance to that in the Fe2([mu]-O)2 diamond core proposed for the methane monooxygenase intermediate Q. The structural differences between {Ar[superscript iPr8]OFe([mu]-O)}2 and {Ar[superscript iPr8]OCo([mu]-O)}2 are reflected in rather differing magnetic behavior. Compound {Ar[superscript iPr8]OCo([mu]-O)}2 is thermally unstable and its decomposition at room temperature resulted in the oxidation of the Ar[superscript iPr8] ligand via oxygen insertion and addition to the central aryl ring of the terphenyl ligand to produce the 5,5'-peroxy-bis[4,6-[superscript i]Pr2-3,7-bis(2,4,6-iPr3-phenyl)oxepin-2(5H)-one]. The structure of the oxidized terphenyl species is closely related to that of a key intermediate proposed for the oxidation of benzene. In Chapter 3, the homoleptic, cobalt(I) alkyl [Co{C(SiMe2Ph)3}]2 was prepared by reacting CoCl2 with [Li{C(SiMe2Ph)3}(THF)] in a 1:2 ratio though the initial intent was to synthesize a dialkyl cobalt (II) complex. Attempts to synthesize the corresponding iron(I) species led to the iron(II) salt [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2]. Both complexes were characterized by X-ray crystallography, UV-vis spectroscopy, and magnetic measurements. The structure of [Co{C(SiMe2Ph)3}]2 consists of dimeric units in which each cobalt(I) ion is [sigma]-bonded to the central carbon of the alkyl group -C(SiMe2Ph)3 and [pi]-bonded to one of the phenyl rings of the -C(SiMe2Ph)3 ligand attached to the other cobalt(I) ion in the dimer. The structure of [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2] features three chlorides bridging two iron(II) ions. Each iron (II) ion is also [sigma]-bonded to the central carbon of a terminal -C(SiMe2Ph)3 anionic ligand. The magnetic properties of [Co{C(SiMe2Ph)3}]2 reveal the presence of two independent cobalt (I) ions with S = 1 and a significant zero-field splitting of D = 38.0(2) cm−1. The magnetic properties of [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2] reveal extensive antiferromagnetic exchange coupling with J = -149(4) cm−1 and a large second-order Zeeman contribution to its molar magnetic susceptibility. Formation of the alkyl [Co{C(SiMe2Ph)3}]2 and the halide complex [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2] under similar conditions is probably due to the fact that Co(II) is more readily reduced than Fe(II). Some other synthetic routes were also attempted to synthesize a dialkyl cobalt (II) complex and they are described in this chapter. Neither [Co(NPh2)2]2 nor cobaltocene reacts with [Li{C(SiMe2Ph)3}(THF)] to afford a dialkyl cobalt (II) complex. Metathesis reactions of cobalt halides with lithium salts of alkyl ligand HCPh2R (R = -Ph or -SiMe3) resulted in the reduction of cobalt (II) to cobalt metal and the coupling of ligands, which indicate that homolytic cleavage of the cobalt-carbon bond was probably involved in the metathesis reactions. Furthermore, in chapter 4, reaction of Sm[N(SiMe3)2]2(THF)2 with two equivalents of bulky aryloxide ligand HOAr[superscript iPr6] (Ar[superscript iPr6] = -C6H3-2,6-(C6H2-2,4,6-[superscript i]Pr3)2) afforded the first monomeric homoleptic solvent-free bis(aryloxide) lanthanide complex Sm(OAr[superscript iPr6])2. The complex was characterized by crystallography, UV-Visible spectrum, IR and magnetically by the Evans' method. The O-Sm-O angle is bent at 111.08(9)̊. The samarium ion in Sm(OAr[superscript iPr6])2 also shows weak interactions with the flanking aryl rings of the terphenyloxide ligands. The complex is paramagnetic at room temperature with magnetic moment of 3.51 [mu]B.
Book Synopsis Direct Synthesis of Coordination and Organometallic Compounds by : A.D. Garnovskii
Download or read book Direct Synthesis of Coordination and Organometallic Compounds written by A.D. Garnovskii and published by Elsevier. This book was released on 1999-08-13 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is devoted to the interaction between elemental metals and (in)organic ligands in different reaction conditions. Metals could be activated for further reactions as cryosynthesis, electrosynthesis and tribosynthesis, some of them with or without ultrasonic and microwave treatment. The kinetics of metal dissolution in various non-aqueous media is discussed in detail. Many methods are used nowadays to synthesize coordination compounds. Metal complexes are obtained mainly by the direct interaction of the components (the ligands and a source of the complex-forming metal), as a result of ligand and metal exchange, and under the conditions of template synthesis, which also include the method of nascent reagents. In these methods the source of the metal is either its salts or carbonyls. At the same time, it has long been known that coordination compounds may be obtained as a result of direct synthesis from zero-valent metals. Methods for the synthesis of complex compounds under the conditions of gas-phase reactions, oxidative dissolution of zero-valent metals in non-aqueous media, and in the solid phase have been developed. These methods have become the basis of a new field in synthetic chemistry - the direct synthesis of coordination and organometallic compounds from zero-valent metals. Particular aspects of the above problem have been described in a series of reviews and monographs. However, on the whole these main parts of the direct synthesis of metal complexes has not been dealt with in the review and monograph publications on coordination chemistry. So, the main objective of this book is to analyze, discuss and generalize the existing information in the area of direct reactions leading to the coordination and organometallic reactions. Some methods of direct synthesis have been developed in the former USSR (in particular, a lot of works on cryosynthesis, pioneered (1972-1973) and recent works on electrosynthesis) but, in spite of their novelty and/or wide applicability, they are practically unknown elsewhere due to the language barrier. Thus, another objective of this book is to acquaint the readers with the mentioned achievements. Every chapter contains the tables which describe all the reported data on direct reaction between metal atoms, metal particles or bulk metals with (in)organic ligans. There are some illustrations also (for example, the scheme of the reactor for gas-phase reaction between metal small particles and &bgr;-diketones).
Book Synopsis Direct Synthesis of Metal Complexes by : B.I. Kharisov
Download or read book Direct Synthesis of Metal Complexes written by B.I. Kharisov and published by Elsevier. This book was released on 2018-04-19 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct Synthesis of Metal Complexes provides in-depth coverage of the direct synthesis of coordination and organometallic compounds. The work is primarily organized by methods, but also covers highly relevant complexes, such as metal-polymer coordination compounds. This updated reference discusses recent developments in cryosynthesis, electrosynthesis, and tribosynthesis (popular as it doesn’t require organic solvents), with special attention paid to ‘greener’ methodologies and approaches. Additionally, the book describes physical methods of zero-valent metal interaction with organic matter, including sputtering, ultrasonic treatment and synthesis in ionic liquids. The book presents completely new content as a follow-up to the 1999 Elsevier Science publication Direct Synthesis of Coordination and Organometallic Compounds that was edited by Dr. Garnovskii and Dr. Kharisov. Covers current methods and techniques of metal interactions with organic media leading to metal chelates, adducts, di- and polymetallic complexes, metal-containing macrocycles, supported coordination compounds (i.e., metal complexes on carbon nanotubes), and more Describes reactivities of distinct forms of elemental metals (powders, sheets, nanoparticles (including a host of less-common metal nanostructures) with organic phase (liquid, solid and gaseous) and water Includes experimental procedures, with examples of direct synthesis, at the end of each chapter
Book Synopsis Late Transition Metal-Carboryne Complexes by : Zaozao Qiu
Download or read book Late Transition Metal-Carboryne Complexes written by Zaozao Qiu and published by Springer Science & Business Media. This book was released on 2012-01-05 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zaozao Qiu shows in this thesis that transition metals can mediate or catalyze the cycloaddition or coupling reactions of carboryne with alkynes or alkenes to afford benzocarboranes, alkenylcarboranes or dihydrobenzocarboranes. These results represent powerful strategies to assemble useful complex molecules from very simple precursors in a single operation. Carboranes have many applications in medicine. However, their unique structures make derivatization difficult and the limited efficient synthetic methods to obtain functional carborane materials have restricted applications of carboranes within a narrow scope. This work breaks a new ground in metal-carboryne chemistry and will have a significant impact on synthetic, cluster and materials chemistry.
Book Synopsis Synthesis of Terminal Transition Metal Pnictide Complexes by Activation of Small Molecules by : Josh Abbenseth
Download or read book Synthesis of Terminal Transition Metal Pnictide Complexes by Activation of Small Molecules written by Josh Abbenseth and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coordination compounds involving metal-nitrogen bonds are a well-developed class of organometallic chemistry. In contrast, the chemistry of the heavier analogues of nitrogen, e.g. phosphorus and arsenic is far less explored. This thesis describes the synthesis and characterization of suitable rhenium and osmium PNP pincer compounds to serve as starting materials for further conversion towards heavy transition metal pnicogen complexes. A square-planar Os(II) PNP pincer complex is reported which features a unique electronic structure and serves as a convenient starting material to synthesize ...
Book Synopsis Synthesis, Characterization, and Reactivity of Transition Metal Complexes Supported by Heteropolydentate Ligation by : Adam Ruddy
Download or read book Synthesis, Characterization, and Reactivity of Transition Metal Complexes Supported by Heteropolydentate Ligation written by Adam Ruddy and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthesis and Characterization of Transition Metal Complexes with Bulky Tin Ligands for Application in Small Molecule Activation by : Veeranna Yempally
Download or read book Synthesis and Characterization of Transition Metal Complexes with Bulky Tin Ligands for Application in Small Molecule Activation written by Veeranna Yempally and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The role of bulky tin ligands in the stabilization of transition metal complexes with electronic unsaturation has been studied to understand the mode of binding of small molecules at an unsaturated metal center. We were able to isolate electronically unsaturated Pt-Sn bimetallic complexes effective in the reversible activation of small molecules including CO, H2, C2H4, and NH3 at room temperature. We have examined the effect of the modification of ligands in Pt-Sn bimetallic complexes for the activation of small molecules and have observed that the Pt(SnBut3)2(CNBut)2 bimetallic complex reversibly activates hydrogen at room temperature both in the solid state and in solution. Similarly, we have also prepared bimetallic Pt-Sn complexes with an NHC carbine ligand which were also shown to activate hydrogen and alkenes reversibly. A bimetallic Fe-Sn cluster complex, Fe2 ([mu]-SnBut2)2(CO)8, was synthesized from the reaction of But3SnH with the Fe2(CO)9 and shown to be selective at activating the benzylic C-H bond of alkylaromatic solvent molecules. The new complexes containing tin have been characterized spectroscopically to gain an insight into the reaction mechanism involved in small molecule activation.
Book Synopsis The Utility of Low-valent Niobium in Small Molecule Activation and the Study of First Row Transition Metal Complexes Supported by Tetradentate Redox Active Ligands by : Valerie Anne Williams
Download or read book The Utility of Low-valent Niobium in Small Molecule Activation and the Study of First Row Transition Metal Complexes Supported by Tetradentate Redox Active Ligands written by Valerie Anne Williams and published by . This book was released on 2014 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt: The low-valent complex (silox)3NbPMe3 (silox = tBu3SiO) was synthesized and tested for reactivity towards small molecules. It was discovered that exposure to CO generated the complexes (silox)3Nb=C=C=O (3-Nb), (silox)3Nb=O (2-Nb), and [(silox)3Nb]2([mu]-C2) (4-Nb) in various ratios depending on reaction stoichiometry. The formation of [(silox)3Nb]2([mu]-CO) (5-Nb) was discovered as a byproduct in most reactions. Treatment of (silox)3NbPMe3 with potassium under a dinitrogen atmosphere afforded the dinitrogen complex (silox)3NbNNNb(silox)3 (8-Nb). Reaction of (silox)3NbCl (10-Nb) with NH3 afforded (silox)3NbIV(NH3)Cl, with ammonia binding parameters of [INCREMENT]H = 20.4 ± 2.3 kcal/mol and [INCREMENT]S = 39 ± 7 e.u. The nickel complex {dmp(PI)2}Ni (dmp(PI)2 = Me2C(CH2=Npy)2) was synthesized and subjected to chemical oxidation and reduction to synthesize a 5membered redox series. Through electronic structure study, it was determined that in these complexes the metal center typically remained NiII, with the possible exception of the cationic complex [{dmp(PI)2}Ni](OTf), and redox changes were primarily ligand-centered. The chemistry of dmp(PI)2 was extended to iron, and {dmp(PI)2}FePMe3 was synthesized. As with the nickel analogue, the complex was determined to be a MII center bound to a dianionic ligand framework, with similar redox behavior as the nickel species. A related tetradentate [beta]-diketiminate-based ligand incorporating two pyridinemethylene units, 2,4-bis[(E)-(2-pyridyl)methylideneamino]pentane (H{nn(PM)2}), was synthesized and metallated to form {nn(PM)2}FeN(TMS)2 (1-N(TMS)2). 1-N(TMS)2 could be further derivatized to form {nn(PM)2}FeX (X = Cl, N3). One of the methylene fragments of the ligand backbone was prone to facile deprotonation and allowed synthesis of {nn(PM)(PI)}FeLL' (LL' = (PMe3)2, (PMe2Ph)2, (PMe3)CO; 2LL') and {nn(PM)(PI)}FeL (L = PMe3, PMePh2, PPh3, CO; 3-L). Electronic structure studies suggested 2-LL' and 3-L existed as FeII metal centers bound to dianionic {nn(PM)(PI)}2-, with strong metal-ligand covalency in 3-L. Oxidation studies on 2(PMe3)2 showed two successive ligand-based 1e- oxidations. The same tetradentate [beta]diketiminate-based ligand was applied to other transition metals of the first row and allowed synthesis of {nn(PM)2}VCl2 (1-VCl2) and {nn(PM)2}Co (1-Co), both of which formed through unusual ligand exchange or disproportionation events, and {nn(PM)(PI)}M (M = Cr, 4-Cr; M = Ni, 4-Ni), which were generated through double deprotonation of the H{nn(PM)2} ligand.
Book Synopsis Preparation, Characterisation and Reactivity of Low Oxidation State d-Block Metal Complexes Stabilised by Extremely Bulky Amide Ligands by : Jamie Hicks
Download or read book Preparation, Characterisation and Reactivity of Low Oxidation State d-Block Metal Complexes Stabilised by Extremely Bulky Amide Ligands written by Jamie Hicks and published by Springer. This book was released on 2018-06-29 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the synthesis and characterization of numerous metal-metal bonded complexes that are stabilized by extremely bulky amide ligands. It provides a comprehensive overview of the field, including discussions on groundbreaking complexes and reactions, before presenting in detail, exciting new findings from the PhD studies. The thesis appeals to researchers, professors and chemistry undergraduates with an interest in inorganic and/or organometallic chemistry.
Book Synopsis Synthesis of Low-coordinate Transition Metal Complexes of the Heavier Group 13 Elements by : Natalie D. Coombs
Download or read book Synthesis of Low-coordinate Transition Metal Complexes of the Heavier Group 13 Elements written by Natalie D. Coombs and published by . This book was released on 2008 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthesis, Characterization, and Reactivity Evaluation of Late Transition Metal-Aluminum Heterobimetallic Complexes Toward Molecular Hydrogen by : Roland Malcolm Charles III
Download or read book Synthesis, Characterization, and Reactivity Evaluation of Late Transition Metal-Aluminum Heterobimetallic Complexes Toward Molecular Hydrogen written by Roland Malcolm Charles III and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The investigation and development of heterobimetallic systems has seen a meteoric surge over the past decade. Generally, these heterobimetallic systems involve two transition metals with distinct properties used together to activate chemical bonds. Many heterobimetallics consist of a soft, low-valent metal and a harder, high-valent metal. The unique electronics afforded by heterobimetallics of this sort can be exploited, yielding access to novel reactivities that may be otherwise inaccessible to a single transition metal. Less studied are heterobimetallic complexes composed of one late transition metal (LTM) and one Lewis-acidic p-block (Group 13) metal. Due to its electropositivity being the highest among Group 13 metals as well as its high earth-abundance, aluminum holds particular interest to the Brewster laboratory. In contrast to their exhaustively investigated boron analogues, the field of aluminum-containing heterobimetallics is relatively uncultivated due to the high reactivity and synthetic difficulty of aluminum species, making isolation and characterization quite challenging. One of the aims of the Brewster lab is to develop heterobimetallic systems comprised of an electron-rich, low-valent transition metal and aluminum to investigate potential synergistic reactivity between both metal centers. In this dissertation, I report the successful synthesis and electronic characterization of myriad novel mono- and heterobimetallic complexes of either iridium or rhodium and aluminumover 35 new complexes in total. Moreover, I detail the ability of selected heterobimetallic complexes to facilitate activation of molecular hydrogen as well as hydrogenolysis, thereby generating alkane gas..
Book Synopsis Synthesis of Heterometallic Zinc-Gold and Lanthanide-Transition Metal Carbonyl Complexes and Reactivity Study of Pentaphosphaferrocene Towards Low-Valent Main Group Species by : Ravi Yadav
Download or read book Synthesis of Heterometallic Zinc-Gold and Lanthanide-Transition Metal Carbonyl Complexes and Reactivity Study of Pentaphosphaferrocene Towards Low-Valent Main Group Species written by Ravi Yadav and published by Cuvillier Verlag. This book was released on 2019-11-27 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work reported in this thesis is divided into three parts. In the first part, the synthesis of Zn-Au heterometallic complexes is described by using bifunctional carboxy-phosphine ligands. The second part of this thesis focuses on redox reactions between divalent lanthanides (LnII) and transition metal (TM) carbonyl complexes for the synthesis of high nuclearity heterometallic complexes. The third and final part of this thesis focuses on reactivity studies of [Cp*Fe(Л5-P5)] with lowvalent main group compounds.
Book Synopsis Design of First-row Transition Metal Bis(alkoxide) Complexes and Their Reactivity Toward Nitrene and Carbene Transfer by : James Bellow
Download or read book Design of First-row Transition Metal Bis(alkoxide) Complexes and Their Reactivity Toward Nitrene and Carbene Transfer written by James Bellow and published by . This book was released on 2016 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: The novel alkoxide ligand [OCtBu2Ph], or [OR], was synthesized in a single step as a lithium salt. It was then reacted with a series of first-row transition metal(II) halides, with widely varying results. Upon reaction with chromium, manganese, iron, or cobalt(II) chloride, dimeric complexes of the form M2(OR)4Li2Cl2 were formed, which displayed rare seesaw geometry at the metal. This unusual geometry was confirmed by various spectroscopic and computational studies. Computational studies also indicate that the steric bulk of the ligand, as well as the inclusion of lithium atoms in the molecules, are what lead to the seesaw geometry. Reaction of [OR] with nickel(II) halides generates monomeric species of the form Ni(OR)2XLi(THF)2 (X = Cl, Br), which display distorted trigonal planar geometry at three-coordinate nickel. Dimerization likely does not occur for nickel due to its smaller size. DFT studies support preference for nickel to form the monomer. Reaction of [OR] with copper(II) halides leads to reduction of the copper center by one electron, generating the tetramer Cu4(OR)4. Reduction of copper(II) by an alkoxide is a novel transformation. Spectroscopic studies to probe the mechanism suggest that Cu(OR)2XLi(THF)2 may be an intermediate prior to reduction. Observation by NMR of the ketone Ph(C=O)tBu and ROH suggest that alkoxide reduces the copper to give an alkoxide radical, which then decomposes via ß-scission. To form the desired bis(alkoxide) system, the halide-containing alkoxide complexes were reacted with thallium(I) hexafluorophosphate. For manganese, iron, and copper, complexes of the form M(OR)2(THF)2 were isolated. The bis(alkoxide) complexes display distorted tetrahedral geometry at the metal, with large RO-M-OR angles. Cyclic voltammetry of these species show that the iron bis(alkoxide) is the most easily reduced of the three.
Book Synopsis Synthesis and Reactivity of Low Valent Transition Metal Alkoxides and Related Compounds by : Kathryn Mary Sanchez
Download or read book Synthesis and Reactivity of Low Valent Transition Metal Alkoxides and Related Compounds written by Kathryn Mary Sanchez and published by . This book was released on 1988 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Catalytic Small Molecule Reduction Using Late Transition Metal Complexes of Carbon and Nitrogen Donor Chelates by : Sopheavy Siek
Download or read book Catalytic Small Molecule Reduction Using Late Transition Metal Complexes of Carbon and Nitrogen Donor Chelates written by Sopheavy Siek and published by . This book was released on 2017 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogenation reactions can be used to store energy in chemical bonds, and if these reactions are reversible that energy can be released on demand. A new bidentate chelating ligand was designed and synthesized for this project, using an N-heterocyclic carbene ring bound directly to a pyridinol ring (NHC-pyOR). This new ligand was used to make iridium complexes that were studied as catalysts for the hydrogenation of CO2 and dehydrogenation of formic acid. For comparison, analogous bipy derived iridium and ruthenium complexes were also tested. In general, the NHC-pyOR complexes demonstrated modest activity, where hydroxyl-pyridines found in the bipy derived systems are more active for CO2 hydrogenation under basic conditions. However, the trends were quite different for formic acid dehydrogenation reaction which will be discussed in Chapter 2. Other ruthenium (II) and iridium (III) complexes of the NHC-pyOR ligand with difference counter anions from above complexes were also synthesized. The ruthenium complexes were tested for their ability to accelerate CO2 (de)hydrogenation, but our studies show that these complexes all undergo transformations in solution and thus they are not true catalysts, but rather pre-catalysts. The use of new tridentate pincer ligands derived from NHC and pyridinol is also described. A new ligand containing (NHC-pyOR-NHC) rings binding to a metal with the pyridinol derivative were synthesized. A series of metal complexes of the type LnM were synthesized (n = 1 and 2; M = Fe2+, Co3+, and Ru2+). Preliminary results of photocatalytic reduction of CO2 to CO show that ruthenium complexes are the most active catalysts followed by cobalt and iron, respectively. The activation of carbon dioxide and nitrite utilizing bio-inspired and proton responsive catalysts were also studied with tris(triazolyl)hydroborate (Ttz) complexes of zinc(II) and copper(II). For the biomimetic zinc complexes for CO2 activation, the synthetic result was found to be greatly depend on the steric bulk of Ttz ligand which will be discussed in detail in Chapter 6. Moreover, the electrochemical reduction of Ttz-Cu(II) complexes in the presence and absence of a proton source shows processes that are relevant to enzymatic nitrite reduction which also will be studied in Chapter 7.
