Synthesis And Spectroscopy Of Lanthanide Halide And High Oxidation State Early Transition Metal Complexes With Neutral Donor Ligands
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Synthesis And Spectroscopy Of Lanthanide Halide And High Oxidation State Early Transition Metal Complexes With Neutral Donor Ligands
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Author : Robert David Bannister
language : en
Publisher:
Release Date : 2020
Synthesis And Spectroscopy Of Lanthanide Halide And High Oxidation State Early Transition Metal Complexes With Neutral Donor Ligands written by Robert David Bannister and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
Disubstituted 1 8 Diaminonaphthalene As Supporting Ligands For High Oxidation State Early Transition Metal And Lanthanide Complexes
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Author : Nathalie Lavoie
language : en
Publisher:
Release Date : 2010
Disubstituted 1 8 Diaminonaphthalene As Supporting Ligands For High Oxidation State Early Transition Metal And Lanthanide Complexes written by Nathalie Lavoie and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with University of Ottawa theses categories.
The Synthesis And Characterization Of Early High Late Low Oxidation State Mixed Metal Organometallic Compounds
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Author :
language : en
Publisher:
Release Date : 1999
The Synthesis And Characterization Of Early High Late Low Oxidation State Mixed Metal Organometallic Compounds written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with categories.
Lanthanides Chemistry And Use In Organic Synthesis
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Author : Shu Kobayashi
language : en
Publisher: Springer
Release Date : 2003-07-01
Lanthanides Chemistry And Use In Organic Synthesis written by Shu Kobayashi and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003-07-01 with Science categories.
With contributions by numerous experts
Oxidation State Roulette
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Author : Brandon Fitchett
language : en
Publisher:
Release Date : 2018
Oxidation State Roulette written by Brandon Fitchett and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
The use of rare and expensive noble metals in the chemical industry as organometallic catalysts has grown exponentially in the past few decades due to their high activity, selectivity and their ability to catalyze a wide range of reactions. With this growth in use has also come a proportional growth in concern as these toxic metals inevitably leach into the environment and their negative effects on public health and our ecosystems are becoming better understood. First-row transition metal catalysts provide both environmental and economic benefits as alternatives to these noble metals due to their lower toxicity and cheaper costs. The two-electron chemistry that makes the noble metals so attractive however, is more challenging to accomplish with first-row transition metals. Intelligently designing the ligand scaffold which surrounds the metal can mitigate or even eliminate some of the shortfalls of these first-row metals. Some key features that should be considered when designing a ligand are: 1) a strong chelating ability so the ligand can stay attached to the metal, 2) incorporation of strong donors to favour low-spin complexes, 3) inclusion of hemilabile groups to allow for substrate activation and metal stabilization throughout various oxidation states, 4) redox activity to be able to donate or accept electrons, and 5) inclusion of Lewis base functionalities which are able to assist the substrate activation. Ligands which incorporate these features are known as bifunctional ligands as they can accomplish more than one function in the catalytic cycle. Developing first-row transition metal complexes containing these ligands may enable these species to replicate the reactivity and selectivity generally associated with the precious metals. Being able to replace the noble metals used in industry with these catalysts would have tremendous environmental and economic benefits. The objective of this thesis is to advance the field of bifunctional catalysis by examining the behaviour of two sterically svelte, tridentate SNS ligands containing hard nitrogen and soft sulphur donors when bonded to cobalt. Previous work with iron provides a template of the ligand behaviour to which cobalt can be compared, allowing us to contrast the effects exerted by the different metals. After an introduction to bifunctional catalysis in Chapter 1, Chapter 2 describes the reactivity of the amido ligand, SMeNHSMe, with precursors ranging from Co(I) to Co(III), all of which yielded the 19e- pseudooctahedral cobalt(II) bis-amido complex, Co(SMeN-SMe)2 characterized by 1H NMR spectroscopy, single-crystal X-ray crystallography and cyclic voltammetry. Although this complex has a similar structure as the Fe analogue, the cobalt bis-amido complex did not exhibit the same hemilabile behaviour that allowed for simple ligand substitution of one of the thioether groups. Instead it reacted reversibly with 2,2'-bipyridine while 1,2-bis(dimethylphosphino)ethane (DMPE) and 2,6-dimethylphenyl isocyanide both triggered additional redox chemistry accompanied by the loss of protonated SMeNHSMe. In contrast, protonation gave the cobalt(II) amido-amine cation, [Co(SMeNSMe)(SMeNHSMe)](NTf2), which allowed for substitution of the protonated ligand by acetonitrile, triphenylphosphine and 2,2'-bipyridine based on 1H NMR evidence. The ability of Co(SMeNSMe)2 to act as a precatalyst for ammonia-borane dehydrogenation was also probed, revealing that it was unstable under these conditions. Addition of one equivalent of DMPE per cobalt, however, resulted in better activity with a preference for linear aminoborane oligomers using ammonia-borane and, surprisingly, to a change in selectivity to prefer cyclic products when moving to methylamine-borane. Chapter 3 delves into the chemistry of the thiolate ligand, SMeNHS, which formed a new 18e- cobalt(III) pseudooctahedral complex, Co(S-NC-)(SMe)(DEPE), from oxidative addition of the Caryl-SMe bond. Scaling up this reaction resulted instead in formation of an imine-coupled [Co(N2S2)]- anion which was characterized by 1H NMR/EPR spectroscopy, single-crystal X-ray diffraction, cyclic voltammetry and DFT studies. The latter revealed an interesting electronic structure with two electrons delocalized in the ligand, demonstrating the non-innocent nature of the N2S2 ligand. While the analogous iron complex proved to be an effective pre-catalyst for the hydroboration of aldehydes with selectivity against ketones, this behaviour was not observed with [Co(N2S2)]- which gave a slower rate and less selectivity. The knowledge acquired from this thesis work has advanced the field of bifunctional catalysis by extending the application of these two SNS ligands from iron to cobalt, revealing unpredictable differences in reactivity between the metals. By comparing the behaviour of these ligands with iron and cobalt, we gain a better understanding of the chemistry that is accessible by these ligands and the applications for which they may be used. This increased knowledge contributes to our long-term goal of replacing expensive and toxic noble metals with more benign first-row transition metals, improving the sustainability of the chemical industry.
Synthesis Characterization And Reactivity Studies Of Low Coordinate Late Transition Metal Complexes And The Preparation And Characterization Of A Low Coordinate Samarium Complex
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Author : Pei Zhao
language : en
Publisher:
Release Date : 2015
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 has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
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.
Dissertation Abstracts International
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Author :
language : en
Publisher:
Release Date : 2002
Dissertation Abstracts International written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Dissertations, Academic categories.
Synthesis And Reactivity Of Lanthanide Transition Metal Polyhydride Complexes
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Author : Daniel Alvarez
language : en
Publisher:
Release Date : 1990
Synthesis And Reactivity Of Lanthanide Transition Metal Polyhydride Complexes written by Daniel Alvarez and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with Rare earth metals categories.
Synthesis Structure And Reactivity Of Transition Metal Complexes Containing P O And N Donor Ligands
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Author :
language : en
Publisher:
Release Date : 2001
Synthesis Structure And Reactivity Of Transition Metal Complexes Containing P O And N Donor Ligands written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Synthesis And Chemistry Of Lanthanide Complexes With Phosphorus Ylides Amides Or Porphyrinate Ligands And Of Transition Metal Complexes With Polydentate Ligands
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Author : Lilu Zhang
language : en
Publisher:
Release Date : 1999
Synthesis And Chemistry Of Lanthanide Complexes With Phosphorus Ylides Amides Or Porphyrinate Ligands And Of Transition Metal Complexes With Polydentate Ligands written by Lilu Zhang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with Ligands categories.