Reactivity of Seven-coordinate Early Transition Metal Isocyanide Complexes PDF Download
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Author: Steve Warner
Publisher:
ISBN:
Category :
Languages : en
Pages : 496
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Author: Steve Warner
Publisher:
ISBN:
Category :
Languages : en
Pages : 496
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Author: Charles Cameron Mokhtarzadeh
Publisher:
ISBN:
Category :
Languages : en
Pages : 434
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This dissertation describes the targeted attempts at the generation of transition metal species that function as precise electronic structure mimics to the well known spin triplet (S =1) metal carbonyls fragments Fe(CO)4 and CpCo(CO). These unsaturated fragments have been shown to display a wide range reactivity, and competency towards important reaction chemistry such as alkane and N2 binding, and E-H bond activation due to a unique interplay of a strong ligand field, formal dn count, and orbital symmetry, rendering these fragments primed for bond activation. Accordingly, ligand architectures that can accurately mimic the ligand field provided by CO to kinetically stabilize these fragments could provide new inroads to novel small molecule activation pathways. To this end, sterically encumbering m-terphenyl isocyanides serve as isolobal ligand surrogates for carbon monoxide (CO). Additionally isocyanides have the added benefit of providing kinetic stabilization by virtue of readily tunable isocyano-R (CN-R) group. The first section of this dissertation describes the synthesis and protonation of an encumbered tetra-isocyanide iron dianion, Na2[Fe(CNArMes2)4] (ArMes2 = 2,6-(2,4,6 --Me3C6H2)2C6H3), which serves as a platform for targeting species of the formulation Fe(CNArMes2)4. It is shown that the reactivity of the electronically unsaturated Fe(CNR)4 fragment upon protonation of Na2[Fe(CNArMes2)4] and subsequent alkylation of Na[HFe(CNArMes2)4], yields the dinitrogen stabilized species Fe(N2)(CNArMes2)4. Fe(N2)(CNArMes2)4 is shown to readily undergo intramolecular C-H activation of the ligand scaffold upon liberation N2 under ambient conditions purportedly through and insipient [Fe(CNArMes2)4] fragment. Further more, ability of Na2[Fe(CNArMes2)4] to facilitate the reductive disproportionation of CO2, in addition to CO2 capture with electrophilic silyl sources is presented culminating in a rare class of low valent Fe-aminocarbyne complexes. The second vignette of this dissertation focuses on the generation of species that mimic the formulation CpCo(L). It is shown that with less encumbering m-terphenyl isocyanides that aggregation akin to the unsaturated carbonyl congeners is realized. Use of encumbering m-terphenyl isocyanides provides access to the three memebered electron transfer series [([mu]2-CNArMes2)2[CpCo]2]n (n = 0,-1, -2). Notably, this series is the first of its kind to span all three ostensible electronic states (e.g. d8-d8, d8-d9, and d9-d9), previously unavailable with other [pi]-acidic ligand frameworks. Additionally this allows for a systematic reassessment of the metal-metal bonding within this class of dimeric species. Evidence is put forth in favor of no M-M bonding interactions occur within these systems and the integrity of the dimeric framework is in fact mitigated through a unique interplay of the metal d-manifold and the isocyanide [pi]*-system. Modulation of the steric profile of the m-terphenyl isocyanide and the Cp unit to Cp* so as to increase the steric pressure provides access to the first reported mono-nuclear Cp*Co(N2)L fragments. It is shown that these species function as viable sources of Cp*Co(CNR) for a number of bond activation processes including Si-H, H-H, and P-P bond scission. Moreover, the reactivity of these species culminates with the isolation of the second example of a structurally authenticated transition metal nitrous oxide (N2O) adduct, which exhibits an unprecedented [eta]2-(N,N) coordination mode to Co. Finally, the reduction of the encumbered Cp*Co(CNArTripp2) (CNArTripp2 2,6-(2,4,6-(i-Pr)3C6H3)2C6H3) fragment provide access to the unique dianion K2[Cp*Co≡CNArTripp2]. It is shown that the dianion K2[Cp*Co≡CNArTripp2] exhibits 3-fold bonding between Co and the isocyanide -Ciso through an extreme case of M-->(CN) [pi]*-back donation and gives rise to the first example of a Co-carbyne complex. The reactivity and electronic structure are presented for K2[Cp*Co≡CNArTripp2] and it is concluded that this reactive dianion behaves as a potent metal based nucleophile and source of [Cp*Co(CNR)]2- for a number of bond activation process.
Author: Myles Joseph Drance
Publisher:
ISBN:
Category :
Languages : en
Pages : 193
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This dissertation details the utilization of anionic, nucleophilic iron complexes supported by m-terphenyl isocyanide and carbonyl ligands to address longstanding questions in organometallic and inorganic chemistry. Chapter 1 offers a brief account of the development of low valent transition-metal chemistry with carbon monoxide (CO) and isocyanides in mononuclear and multinuclear systems. Metal carbonyl clusters gained popularity as molecular surrogates for reactive sites on heterogeneous catalyst surfaces, and some successes and shortcomings of this cluster-surface analogy are revisited in Chapter 2. The synthesis and reactivity of the tetra-iron nitrido cluster [Fe([mu]4-N)(CO)8(CNArMes2)4]- (ArMes2 = 2,6-(2,4,6-Me3C6H2)2C6H3) is contrasted with the less electron-rich all-carbonyl congener [Fe([mu]4-N)(CO)12]-. Ligand substitution is shown to impart nucleophilicity to the interstitial nitride, and this characteristic enables rational cluster expansion with main-group and transition-metal ions to yield unsaturated sites. The resulting clusters were found to display surface-like reactivity through coordination-sphere-dependent atom rearrangement and metal-metal cooperativity. The remaining three chapters stem from K2[Fe(CO)2(CNArTripp2)2] (ArTripp2 = 2,6-(2,4,6-(i-Pr)3C6H2)2C6H3). In Chapter 3, this metalate is used to generate Fe(BF)(CO)2(CNArTripp2)2, the first stable terminal fluoroborylene complex. Importantly, the isoelectronic species Fe(N2)(CO)2(CNArTripp2)2 and Fe(CO)3(CNArTripp2)2 are also described allowing for the direct comparison of neutral 10 valence-electron ligands. Single-crystal X-ray diffraction, nuclear magnetic resonance, infrared, and Mössbauer spectroscopic studies demonstrate that the terminal BF ligand possesses particularly strong s-donor and p-acceptor properties in accord with theoretical predictions. Density functional theory and electron-density topology calculations support this conclusion. The reactivity of Fe(BF)(CO)2(CNArTripp2)2 is discussed in Chapter 4. Like all terminal borylene ligands, coordinated BF is shown to be electrophilic at boron, forming Lewis acid-base adducts with various nucleophiles. However, the fluoroborylene ligand can be derivatized further than other borylenes and converted stepwise into aminoborylene and iminoboryl moieties. Additionally, BF can be transformed directly to the oxoboryl anion [BO]-. The last chapter presents efforts toward an analogue of the unsaturated binary metal carbonyl Fe(CO)4. Unusual solvent binding and bond activations suggest that Fe(N2)(CO)2(CNArTripp2)2 may indeed serve as a masked functional analogue of Fe(CO)4.
Author: V. Nenajdenko
Publisher: John Wiley & Sons
ISBN: 3527652558
Category : Science
Languages : en
Pages : 615
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The efficacy of isocyanide reactions in the synthesis of natural or naturallike products has resulted in a renaissance of isocyanide chemistry. Now isocyanides are widely used in different branches of organic, inorganic, coordination, combinatorial and medicinal chemistry. This invaluable reference is the only book to cover the topic in such depth, presenting all aspects of synthetic isonitrile chemistry. The highly experienced and internationally renowned editor has brought together an equally distinguished team of authors who cover multicomponent reactions, isonitriles in total synthesis, isonitriles in polymer chemistry and much more.
Author: Antonio Laguna
Publisher: John Wiley & Sons
ISBN: 3527623760
Category : Science
Languages : en
Pages : 525
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Filling a gap in our systematic knowledge of gold, this monograph covers the fundamental aspects, while also considering new applications of gold compounds in catalysis, as nanoparticles, and their potential application as luminescent compounds. Written by an eminent team of authors from academia, the book analyzes the current status of gold chemistry, its special characteristics, oxidation states and main type of complexes, before going on to look at the synthesis of supramolecular aggregates due to the formation of gold-gold, gold-metal interactions or other secondary bonds. Final sections deal with LEDs, solvoluminescent and electroluminescent materials, liquid crystals and catalysis. While of interest to advanced chemistry students, this book is also useful for researchers interested in the chemistry of gold and its applications, as well as those involved in metal-metal interactions, heteronuclear chemistry or in the optical properties of coordination compounds.
Author: Thomas R. Porter
Publisher:
ISBN:
Category :
Languages : en
Pages : 179
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Reactions involving transition metals and organic free radicals are critically important in a variety of chemical and biological processes. Because of their prevalence, there is a fundamental interest in better understanding these types of reactions to fully realize their potential for new applications. The work presented in this dissertation describes the free radical reactivity and thermochemistry of several different transition metal systems with stable organic radicals. Chapter 1 provides an introduction to transition metal reactivity involving organic free radicals. Chapter 2 describes the catalytic disproportionation of a hydroxylamine by (TMP)Fe[superscript III]-OH (TMP = meso-tetramesityl porphyrin) and some of the radical reactions that make up the catalytic cycle. Chapter 3 describes the preparation, structural characterization and thermochemistry of a previously unreported stable organic radical, [superscript t]Bu2NPArO* (2,6-di-tert-butyl-4-(4'-nitrophenyl)phenoxyl). Chapter 4 describes the preparation of several [Tp[superscript tBu]Cu[superscript II]]+ (Tp[superscript tBu] = hydro-tris(3-tert-butyl-pyrazolyl)borate) and [Tp[superscript tBuMe]Cu[superscript II]]+ (Tp[superscript tBu]Me = hydro-tris(3-tert-butyl-5-methyl-pyrazolyl)borate) alkoxide compelxes as models for potential intermediates in copper/radical alcohol oxidation catalysis. Treating these complexes with stable radicals such a [superscript t]Bu3ArO* (2,4,6-tri-tert-butyl-phenoxyl) did not result in alkoxide oxidation despite having a large driving force. From these studies, we conclude driving force is not a primary predictor for copper/radical alcohol oxidation. Chapter 5 discusses the coordination chemistry of [Tp[supercscript tBu]Cu[superscript II]]+ and [Tp[superscript tBu]Zn[superscript II]]+ with 4-nitro-phenols. With the bulky 2,6-disubstituted 2,6-di-tert-butyl-4-nitro-phenoxide, coordination to either metal occurs through a nitronate resonance form. The 2,6-unsubstituted 4-nitro-phenol binds through the phenoxide resonance form. Chapter 6 highlights the large kinetic barrier for ketone reduction or oxidation by titanocene(III/IV) and the hydrogen atom donor/acceptor, [superscript t]Bu3ArO(-H). Finally, Chapter 7 describes the selective and stoichiometric reduction of aromatic and aliphatic nitro groups by photoreduced titanium dioxide nanoparticles in acidic aqueous solutions. From thermochemical analysis, it is likely that these reactions proceed through a rate determining H+/e- transfer.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 992
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Author: Marc John Andrew Johnson
Publisher:
ISBN:
Category :
Languages : en
Pages : 480
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Author: LeGrande Mancel Slaughter (III)
Publisher:
ISBN:
Category :
Languages : en
Pages : 416
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Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 754
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