Metallic Iodine Research Articles

Cationic monocyclooctatetraenyl-lanthanoid complexes derived from metallic lanthanoid: crystal structures of [Sm( η8−C 8H 8)(hmpa) 3]I and [Sm( η8−C 8H 8)(hmpa) 3][Sm( η8−C 8H 8) 2] (HMPA = hexamethylphosphoric triamide)

Addition of an excess hexamethylphosphoric triamide (abbr. HMPA) to a neutral complex SmI( ν 8−C 8H 8(thf) ( 1) (C 8H 8 = 1,3,5,7-cyclooctatetraene), which was prepared by a direct reaction of metallic samarium with C 8H 8 in the presence of iodine in THF, afforded a cationic samarium complex [Sm( η 8−C 8H 8)(hmpa) 3]I ( 2). Complex 2 can also be prepared by a simple one-pot reaction of stoichiometric amounts of metallic samarium, cyclooctatetraene, and iodine in the presence of an excess HMPA at 50°C. With a catalytic amount of iodine, ionic complexes of general formula Ln(η 8− C 8 H 8)( hmpa) n][ Ln(η 8− C 8 H 8) 2] [ Ln = La and n = 4 ( 6); Ln = Sm and n = 3 ( 7) ] were obtained by treating metallic lanthanum or samarium, respectively with cyclooctatetraene in the presence of HMPA. The structure of the diamagnetic complex 6 as well as the paramagnetic complexes 2 and 7 was determined by 1H NMR spectroscopy. Crystal structures of 2 and 7 were revealed by X-ray analyses, indicating that these complexes comprised of a cationic [Sm( η 8−C 8H 8)(hmpa) 3] + and an anionic part; for 2 and 7 being I − and [Sm( η 8−C 8H 8) 2] −, respectively.

ChemInform Abstract: Metallic Samarium and Iodine in Alcohol. Deacylation and Dealkyloxycarbonylation of Protected Alcohols and Lactams.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Metallic Samarium and Iodine in Alcohol. Deacylation and Dealkyloxycarbonylation of Protected Alcohols and Lactams

Metallic Samarium and Iodine in Alcohol. Deacylation and Dealkyloxycarbonylation of Protected Alcohols and Lactams

ChemInform Abstract: Metallic Samarium and Iodine in Alcohol. Selective 1,4‐Reduction of . alpha.,β‐Unsaturated Carboxylic Acid Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Metallic Samarium and Iodine in Alcohol. Selective 1,4-Reduction of α,β-Unsaturated Carboxylic Acid Derivatives

Olefinic double bond of various α,β-unsaturated carboxylic acid derivatives (ester, amide, nitrile, carboxylic acid) is reduced with metallic samarium and iodine to the corresponding saturated products in high yields in alcohol at room temperature under argon.

Reduction of nitrobenzene to aniline with carbon monoxide and water

Modified catalyst systems composed of palladium or its chloride and co-catalysts such as FeCl3, Fe2O3, metallic Fe-powder, metallic Fe-wire net, iodine, pyridine or aniline, applied in the reduction of nitrobenzene to aniline in the presence of carbon monoxide and water are described. The reaction proceeds at 150–180 °C and 2.5–7 MPa gauge pressure. After 1–7 h the reaction was complete, reaching nitrobenzene conversions of 98–100%. Selectivity of the reaction with respect to aniline was also 100%.

The pressure-induced superconductivity of iodine

The superconductivity of metallic iodine is observed at temperatures below 1.2 K under pressures above 28 GPa by magnetization and electrical resistance measurements. The pressure dependence of the superconducting transition temperature is studied up to 74 GPa. This is the first observation of the superconductivity of the molecular-dissociated monatomic metal.

Hall Effect of Iodine in High Pressure

The Hall coefficient of metallic iodine is measured in pressures up to 74 GPa at room temperature and in 30 GPa at 4.2 K. The carrier of the pressure-induced metallic iodine is found to be a hole in agreement with the theoretical prediction.

Optical, x-ray, and band-structure studies of iodine at pressures of several megabars.

Optical-reflectivity and x-ray-diffraction techniques have been used to determine the electronic properties and structure of iodine to 181 and 276 GPa, respectively, in the diamond-anvil cell. X-ray measurements were performed by energy dispersive diffraction with synchrotron radiation. Monatomic metallic iodine transforms to an fcc structure at 53 GPa that remains stable to the maximum pressure. At 276 GPa, the volume compression V/${\mathit{V}}_{0}$ is 0.324. Reflectivity data are consistent with a strong metallic character in iodine from 19 to 181 GPa. The linear muffin-tin orbital method has been used to calculate the equation of state to 500 GPa and to model the reflectivity of iodine at high pressures.

Influence of Defects on Ferroelastic Phase Transition in InI Single Crystals

InI single crystals (space group D172h) are typical layered A 3Β7 compounds with a pronounced anisotropy of the crystalline stucture and the corresponding optical properties [1-5]. At the same time, the recent revelation of the low temperature phase transitions in these crystals [6, 7] can present them as convenient model objects for the creation of phase transitions theory in high anisotropy media including those with the incommensurate phase. In the circumstances, it is very substantial that similar twodimensional systems are most susceptible to the appearance of the translational symmetry perturbations of different kind, above all at the expense of appearance of defects, dislocations and vacancies. The last ones are in particular fashion exhibited in modulated superstructures [8]. The goal of this work is to describe the influence of the defect subsystem on phase transitions in InI single crystals, because the layering of structure allows one to control smoothly the corresponding parameters. The initial samples were synthesized using reaction between the pure metallic indium and iodine in a hermetical quartz ampoule. After the band cleaning and distillation in the vacuum, single crystals have been grown by the Bridgman method [9]. Independently of crystal perfection all the cleaved monocrystalline specimens possessed mirror surfaces of high quality in αc-plane, which did not require additional polishing. The stuctural parameters were checked using the X-ray DROΝ-05 diffractometer. The temperature measurements were performed in the range 4.2-500 K and were stabilized within 0.1-0.2 K•min -1 . The Senarmon method (λ = 0.6328 μm) was used for measuring of the piezooptical constants. Testing of samples quality was performed by the X-ray method. The broadening of X-ray satellite reflexes permits to select crystals of different quality. To obtain smooth change of the specimens quality, they were annealed in non-inertial

Strongly correlated electronic ground states in metals near the metal-insulator transition

The model in which positive ions in a metal are smeared into a uniform neutralizing background in which interacting electrons move is first considered at some length, especially rather near to the metal-insulator (Wiper) transition. Properties considered carefully are (a) the electronic momentum distribution as a function of background density, and (b) the pair correlation function. Features connected with both the long-range Coulombic repulsion and the transition from delocalized to localized behaviour will be highlighted in terms of (a) and (b) above. The possible use of this model as a reference state against which to consider the alkali metals, in both normal and expanded form, will then be discussed. In Na, the importance of 3s–3p hybridization will be emphasized, the Heisenberg model providing a surprisingly useful account of some bulk properties. Diffraction evidence on the degenerate electron assembly in molten Na and K will be considered in support of pronounced metallic bonding. Expanded Cs along the coexistence curve will next be treated, especially the observed magnetic susceptibility which changes from Fermi liquid behaviour to Curie-Weiss form as the critical point is approached. The crossover point is discussed in terms of heavy fermion theory and is shown to contain information about the discontinuity of the electronic momentum distribution at the Fermi surface. This discontinuity is much smaller than that in jellium (the smeared ion model above) and testifies to the importance of the electron-ion interaction at this density, which cannot be treated perturbatively. Finally, the possibility of the co-existence of molecules in metallic phases is considered, with particular reference to metallic hydrogen and metallic iodine near the metal-insulator transition. For the latter, experimental evidence can leave little doubt that there is at least a limited range of pressures over which the metallic ground state of iodine contains I2 molecules, and some discussion of this strongly correlated state will be included.

Diffusion of iodine in lead telluride

AbstractBy using the non‐stationary thermal‐probe method, investigations were carrieed out on the distribution of the coefficient of thermal electromotive force along the depth of monocrystals of lead telluride, subjected to isothermal saturating annealing in vapours of alloying compositions. The alloying composition consisted of powdered lead telluride, synthesized by the iodide method, and contained elevated concentration of the metallic component and iodine. The PbTe monocrystals were obtained from the vapour phase and had a natural cut. The results of the investigations testify to considerable changes in the concentration of the electrically active proper defects within the entire volume of the crystals, this being obviously connected with diffusion of vacancies from the crystal volume.

Pressure-induced face-centered-cubic phase of monatomic metallic iodine.

An x-ray diffraction study of solid iodine at room temperature has revealed that it undergoes a new phase transition at 55\ifmmode\pm\else\textpm\fi{}2 GPa from the face-centered-tetragonal to -cubic phases in its monatomic metallic state. This is the first observation of the fcc Bravais lattice realized in diatomic molecular crystals. Such an isotropic fcc structure is ultimately accomplished after three successive transitions, two of which are the molecular dissociation at 21 GPa and the orthorhombic-to-tetragonal transition at 43 GPa previously observed.

Pressure-induced monatomic tetragonal phase of metallic iodine

An x-ray diffraction study of solid iodine at room temperature has revealed that it undergoes a new phase transition at about 45 GPa from the body-centered-orthorhombic to -tetragonal lattices in its monatomic metallic phase, in addition to the previously-known molecular-to- monatomic transition at 21 GPa. No appreciable discontinuity was observed in the unit cell volume across the transition pressure. This fact leads to an implication of the second order transition. An extrapolation of the present data also implies that a face-centered cubic phase is realized at a much lower pressure than previously predicted.

Electrical Properties of High-Pressure Metallic Modification of Iodine

The electrical resistance up to 250 kbar and down to 1.7 K, and the thermoelectric power up to 250 kbar at room temperature have been measured in iodine using a diamond-anvil cell. The resistance decreases rapidly and continuously with increasing pressure. The resistance anomaly has been found at 225 kbar and room temperature. The resistive characteristic temperature θ in the Gruneisen-Bloch equation is 225 K for metallic iodine at 235 kbar, The thermoelectric power decreases from a large positive value to a small positive one with increasing pressure and is +4±3 µV/deg at 240 kbar. These electrical properties have been discussed in relation to the structural change induced by pressure.

Photodecomposition of Bil3 films

The effect of illumination on the transmittance and the structure of Bil3 films was investigated. Photoexcitation was found to induce structural variation and decomposition of the films into metallic bismuth and free iodine. Moreover, measurements of the electrical conductivity during heating show thermal decomposition of the films and it was found that the temperature of decomposition depends on the thickness of the film.

Observation of Molecular Dissociation of Iodine at High Pressure by X-Ray Diffraction

Metallic iodine in the high-pressure phase above P/sub t/=21 Gpa is found to form a body-centered orthorhombic Bravais lattice. Hence, pressure-induced molecular dissociation takes place at P/sub t/.

ChemInform Abstract: IODINE AT HIGH PRESSURES AND LOW TEMPERATURES

AbstractDer spezifische Widerstand von Iod wird bei Drücken von 80‐280 kbar und Temp. von 300‐2.6 K gemessen.

Iodine at high pressures and low temperatures

Using a cryogenic clamp-type high pressure apparatus, the electrical resistance behavior of iodine was studied for pressures from 80 to 280 kbar and temperatures from 300 to 2.6 °K. The resistivity of iodine approaches metallic values for pressures higher than 130 kbar. No superconductivity is observed in metallic iodine either in the molecular phase below 210 kbar or in the monatomic phase up to 280 kbar.

Normal conductivity and superconductivity of an A1-type iodine phase

A metallic A1-type iodine modification exhibiting soft superconductivity was quench-deposited on CaO or SrO. The normal resistivity, superconducting transition temperature and critical magnetic field decrease with increasing thickness. On heating, the ordinary non-metallic diatomic structure is restored.