Peter B. Hitchcock

Bio: Peter B. Hitchcock is an academic researcher from University of Sussex. The author has contributed to research in topics: Crystal structure & Trimethylsilyl. The author has an hindex of 68, co-authored 1313 publications receiving 28245 citations. Previous affiliations of Peter B. Hitchcock include Kingston University & Instituto Superior Técnico.

Hydrogen bonding in imidazolium salts and its implications for ambient-temperature halogenoaluminate(III) ionic liquids

Abstract: The salts [emim]X (X = Br or I, emim = 1-ethyl-3-methylimidazolium) and [emim][AlBr4] have been prepared as solid-state models of the [emim]X–AlX3(X = Cl or Br) ionic liquid systems. All three have been characterised crystallographically. The salts [emim]X (X = Br or I) are isomorphous and are composed of ions in an extended hydrogen-bonded network. The implications of these results for both the structure and solvent properties of the ionic liquids are discussed.

Structural Chemistry of 1,2 Dilauroyl-DL-phosphatidylethanolamine: Molecular Conformation and Intermolecular Packing of Phospholipids

Abstract: Crystals of 1,2 dilauroyl-DL-phosphatidyl-ethanolamine:acetic acid are monoclinic with a = 462, b = 777, c = 995 A, β = 920°; space group P21/c The structural analysis, based on the visual estimates of 1467 reflection intensities, was achieved by direct methods, and least squares analysis convergence was to R1 = 028 There are marked differences between the observed molecular conformation and those that have been predicted theoretically The mean planes containing the lipid chains are essentially parallel to one another; the phosphodiester moiety has a double gauche conformation, while intermolecular hydrogen bonding modifies the conformation that could be anticipated for an isolated phosphatidylethanolamine molecule The intermolecular packing produces the classical lipid bilayer structure, adjacent lipid bilayers being separated by acetic acid molecules of crystallization The hydrocarbon chain packing can be considered either as a quasi-hexagonal type or as a complex orthorhombic subcell arrangement One-dimensional electron density profiles across the lipid bilayer at increasing resolution clearly demonstrate the origin of features present on the low resolution profiles of both model and natural membranes

Preparation and characterization of C 60 Br 6 and C 60 Br 8

Abstract: BUCKMINSTERFULLERENE (C60) is much more reactive than was originally anticipated, because resonance structures that place double bonds in the pentagonal rings are energetically unfavourable1 and lead to restricted electron delocalization. C60 therefore behaves as an electron-deficient 'super-alkene' rather than as a 'super-aromatic', as demonstrated by the addition of osmium tetroxide2, platinum3, dipolar molecules4, alkyl radicals5and amines6. Reaction of anions derived from C60 with iodomethane results in up to 24 methyl groups becoming attached to the cage, although compounds containing either eight or six methyl groups are dominant in the mass spectrum7. Here we report the synthesis of crystalline C60Br6 (which forms magenta plates) and C60Br8 (dark brown prisms) by mixing solutions of C60 with bromine. The structures of these compounds, which contain occluded bromine when precipitated from the brominating medium, have been determined by single-crystal X-ray diffraction. Reaction of C60 with bromine in the absence of solvent gives C60Br24 (which also contains occluded bromine). We propose a configuration for C60Br24 (and sterically hindered C60X24 compounds) based on that for C60Br8. On being warmed in solution, C60Br6 rearranges and disproportionates to C60Br8, and all three bromo derivatives revert to C60 on strong heating. These results provide an insight into the pattern of addition of bulky reagents to C60.

Reductive Cyclotrimerization of Carbon Monoxide to the Deltate Dianion by an Organometallic Uranium Complex

Abstract: Despite the long history of the Fischer-Tropsch reaction, carbon monoxide has proven remarkably resistant to selective homologation under mild conditions. Here, we find that an organouranium(III) complex induces efficient reductive trimerization of carbon monoxide at room temperature and pressure. The result is a triangular, cyclic C3O32-, or deltate, dianion held between two uranium(IV) units. The bonding within the C 3O32- unit and its coordination to the two U centers have been analyzed by x-ray diffraction and density functional theory computational studies, which show a stabilizing C-C agostic interaction between the C3 core and one U center. Solution nuclear magnetic resonance studies reveal a rapid equilibration of the deltate unit between the U centers.

Lanthanum does form stable molecular compounds in the +2 oxidation state.

Abstract: Getting down to business: Reduction of the LaIII tricyclopentadienide complex [LaCp′′3] (Cp′′=η5-1,3-(SiMe3)2C5H3) by K and [18]crown-6 or [2,2,2]cryptand produced thermally stable mononuclear crystalline lanthanate(II) salts. The La +2 oxidation state in these complexes was confirmed both in solution (EPR) and the solid state (EPR, SQUID, X-ray diffraction) and was supported by a computational study.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Ionic Liquids-New "Solutions" for Transition Metal Catalysis.

Abstract: Ionic liquids are salts that are liquid at low temperature (<100 degrees C) which represent a new class of solvents with nonmolecular, ionic character. Even though the first representative has been known since 1914, ionic liquids have only been investigated as solvents for transition metal catalysis in the past ten years. Publications to date show that replacing an organic solvent by an ionic liquid can lead to remarkable improvements in well-known processes. Ionic liquids form biphasic systems with many organic product mixtures. This gives rise to the possibility of a multiphase reaction procedure with easy isolation and recovery of homogeneous catalysts. In addition, ionic liquids have practically no vapor pressure which facilitates product separation by distillation. There are also indications that switching from a normal organic solvent to an ionic liquid can lead to novel and unusual chemical reactivity. This opens up a wide field for future investigations into this new class of solvents in catalytic applications.

Applications of ionic liquids in the chemical industry

Abstract: In contrast to a recently expressed, and widely cited, view that “Ionic liquids are starting to leave academic labs and find their way into a wide variety of industrial applications”, we demonstrate in this critical review that there have been parallel and collaborative exchanges between academic research and industrial developments since the materials were first reported in 1914 (148 references)

Chemical Redox Agents for Organometallic Chemistry

Abstract: 1. Advantages of Chemical Redox Agents 878 2. Disadvantages of Chemical Redox Agents 879 C. Potentials in Nonaqueous Solvents 879 D. Reversible vs Irreversible ET Reagents 879 E. Categorization of Reagent Strength 881 II. Oxidants 881 A. Inorganic 881 1. Metal and Metal Complex Oxidants 881 2. Main Group Oxidants 887 B. Organic 891 1. Radical Cations 891 2. Carbocations 893 3. Cyanocarbons and Related Electron-Rich Compounds 894