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Significant strides have recently been made involving organometallic modeling of hydrodesulfurization (HDS). These studies have typically utilized late transition metals with high d-electron counts. This thesis focuses on three areas, (i) the synthesis of high oxidation state metal-oxo derivatives of thiophene, (ii) the exploration of the reactivity of the carbon-sulfur bond in condensed thiophenes, and (iii) the discovery of a new polymerization technique for the preparation of polythiophenes. The treatment of thienyllithium with Re(CO)$\sb5$Br followed by PPh$\sb3$ affords the acyl complex cis-$\rm(CO)\sb4(PPh\sb3)Re(C(O)C\sb4H\sb3S).$ A similar pentacarbonyl, $\rm(CO)\sb5Re(C(O)C\sb4H\sb3S),$ complex can be made via the treatment of NaRe(CO)$\sb5$ with thienoylchloride and can be decarbonylated to give $\rm(CO)\sb5Re(C\sb4H\sb3S).$ $\rm(CO)\sb5Re(C\sb4H\sb3S),$ which can be more conveniently made by the treatment of Re(CO)$\sb5$Br with ZnCl$\rm(C\sb4H\sb3S),$ is stable with respect to moisture but decomposes in the presence of strong acids to afford thiophene. Treatment of $\rm ReOCl\sb3(PPh\sb3)\sb2$ with thienyllithium reagents afforded Li(THF)$\rm\sb{n}$,ReO(thienyl)$\sb4$, where thienyl is 2-$\rm C\sb4H\sb3S,$ 2-$\rm MeC\sb4H\sb2,$ 2-$\rm C\sb8H\sb5S$ (benzothienyl), and 2-$\rm C\sb{12}H\sb7S$ (dibenzothienyl). Electrochemical studies demonstrate that these Re(V) complexes undergo oxidation at mild potentials. Crystallographic analyses of $\rm Li(THF)\sb3ReO(C\sb4H\sb3S)\sb4$ and $\rm Li(THF)\sb4ReO(C\sb8H\sb5S)\sb4$ indicate a square pyramidal Re center with the four thienyl ligands tilted in a pinwheel arrangement. The (ReO(thienyl)$\sb4\rbrack\sp{-}$ compounds decompose in the presence of water to give thiophene and oxidatively coupled organic compounds in the presence of oxygen. Attempts at electrophilic substitution at the oxygen with trimethylsilyl chloride afforded 2-$\rm(Me\sb3Si)C\sb4H\sb3S.$ The reaction of 2,2$\sp\prime$-Li(LiS)C$\sb{12}$H$\sb8$ with $\rm(C\sb5H\sb5)\sb2TiCl\sb2$ gave the metallacyclic complex $\rm(C\sb5H\sb5)\sb2TiSC\sb{12}H\sb8$ (1). DNMR studies showed that 1 is stereochemically nonrigid. The structure of the $\rm MeC\sb5H\sb4$ analog of 1 was determined by single crystal X-ray diffraction. Compound 1 decomposes photolytically to yield dibenzothiophene and a $\rm(C\sb5H\sb5)\sb2Ti$ species. An attempt to generate 1 via the double metalation of 2-phenylbenzenethiol with followed by $\rm(C\sb5H\sb5)TiCl\sb2$ gave $\rm(C\sb5H\sb5)\sb2TiS\sb2C\sb{24}H\sb{16}$ (2). Single crystal X-ray diffraction indicated that 2 is a complex of the 2,2$\sp\prime$dimercapto-3,3$\sp\prime$-diphenylbiphenyl (2,2$\sp\prime$-(LiS)$\sb{2}$-3,3$\sp\prime$-$\rm Ph\sb2C\sb{12}H\sb6)$ ligand. Electrochemical studies of the new complexes demonstrated that the Ti$\rm\sp{IV}$ to Ti$\rm\sp{III}$ reduction is reversible. The treatment of thiophene with TiCl$\sb4$/HX (X = OTf, Cl) results in polymerization to generate material having the empirical formula of $\rm C\sb{4n}H\sb{4n}S\sb{n}$, and molecular weights of $\rm M\sb{n}\sim1782$ daltons. NMR and IR studies suggests that the polymer is comprised of a combination of sp$\sp2$ and sp$\sp3$ carbon centers and FAB-MS experiments indicate chain lengths that vary by units of $\rm C\sb4H\sb4S.$ These polymers can coordinate to TiCl$\sb4$ and can be dehydrogenated by quinones. Efforts to polymerize substituted thiophenes afforded oligomers.
Advances and applications of nanosized catalysts Over the last five years, tremendous advances have been made in heterogeneous catalysis. In particular, catalysts' design from the bulk to nano-scale (1-100 nm), with desirable active sites, has received great attention in current catalysis research with the aim to fill the gap between homogeneous and heterogeneous catalysis. This volume focuses on applications of nanosized catalysts. Articles describe characterization, synthesis, and applications in biomass conversion, auto-exhaust purification, selective oxidation/hydrogenation, syngas conversion, and other important reactions. Readers will find examples of catalysts designed to be tunable for specific outcomes, inspiring their research. Scientists and engineers in chemistry, materials science, nanotechnology, and chemical engineering will find this volume useful.
Here, all aspects of the topic are presented in a compact manner. The book is clearly structured, and divided into two sections -- asymmetric synthesis of heterocycles containing only one nitrogen and that of those with more than one nitrogen as a heteroatom -- such that the necessary information may be found at a glance. The international team of authors provides important experimental procedures, including industrial applications. Essential for synthetic chemists in pharmaceutical and agrochemical chemistry.
Heterocyclic chemistry is the biggest branch of chemistry covering two-thirds of the chemical literature. Aromaticity in Heterocyclic Compounds covers hot topics of frontier research summarized by reputed scientists in the field.
During the last decade, fullerenes and carbon nanotubes have attracted special interest as new nanocarbons with novel properties. Because of their hollow caged structure, they can be used as containers for atoms and molecules, and nanotubes can be used as miniature test-tubes. Chemistry of Nanocarbons presents the most up-to-date research on chemical aspects of nanometer-sized forms of carbon, with emphasis on fullerenes, nanotubes and nanohorns. All modern chemical aspects are mentioned, including noncovalent interactions, supramolecular assembly, dendrimers, nanocomposites, chirality, nanodevices, host-guest interactions, endohedral fullerenes, magnetic resonance imaging, nanodiamond particles and graphene. The book covers experimental and theoretical aspects of nanocarbons, as well as their uses and potential applications, ranging from molecular electronics to biology and medicine.
This book describes techniques of synthesis and self-assembly of macromolecules for developing new materials and improving functionality of existing ones. Because self-assembly emulates how nature creates complex systems, they likely have the best chance at succeeding in real-world biomedical applications. • Employs synthetic chemistry, physical chemistry, and materials science principles and techniques • Emphasizes self-assembly in solutions (particularly, aqueous solutions) and at solid-liquid interfaces • Describes polymer assembly driven by multitude interactions, including solvophobic, electrostatic, and obligatory co-assembly • Illustrates assembly of bio-hybrid macromolecules and applications in biomedical engineering
R.N.IBBETT This book provides a source of information on all major aspects of NMR spectroscopy of synthetic polymers. It represents a deliberate attempt to pull together the numerous strands of the subject in a single comprehensive volume, designed to be readable at every scientific level. It is intended that the book will be of use to the vast majority of polymer scientists and NMR spec troscopists alike. Readers new to NMR will find extensive information within the book on the available techniques, allowing full exploration of the many polymer science applications. Readers already established within a branch of NMR will find the book an excellent guide to the practical study of polymers and the inter pretation of experimental data. Readers who have specialised in polymer NMR will find the book a valuable dictionary of proven methodologies, as well as a guide to the very latest developments in the subject. Workers from all of the main branches of polymer NMR have been invited to contribute. Each chapter therefore contains information relating to a parti cular investigative topic, indentified mainly on the basis of technique. The book is loosely divided between solution and solid-state domains, although the numerous interconnections confirm that these two domains are parts of the same continuum. Basic principles are explained within each chapter, combined with discussions of experimental theory and applications. Examples of polymer investigations are covered generously and in many chapters there are discussions of the most recent theoretical and experimental developments.