Eric L. Short

Application of solvent extraction to the refining of precious metals IV. Practical and structural aspects of the separation of rhodium, palladium, iridium and platinum with organic sulphoxides

Abstract Distribution isotherms have been determined radiometrically for the extraction of Pd II , Pt IV , Rh III and Ir III,IV from aqueous HCl solutions by organic sulphoxides in 1,1,2-trichloroethane (TCE). Partition measurements were also made using two different dialkyl sulphides in TCE. A practical scheme for the separation of the precious metals involving di- n -heptyl sulphoxide (DHSO) is proposed. The nature of the metal-ion species participating in the extraction systems and the chemical bonding in such species have been investigated using physical, spectroscopic, and theoretical methods.

Borate complexation with pentitols: A study by 11B-n.m.r. spectroscopy and MNDO semi-empirical LCAO-MO calculations

Abstract The complexation of borate ions and xylitol, ribitol, and arabinitol in aqueous solution at high pH has been studied by 11 B-n.m.r. spectroscopy. Stability constants of the various complexes have been calculated by an iterative method and complemented by MNDO calculations.

A study of the complexes of borate ions and some cyclitols using 11B-n.m.r. spectroscopy

Abstract Complexes between borate ion and cyclohexane- cis -1,2-diol, cyclohexane- cis , cis -1,3,5-triol, and myo - and epi -inositol have been investigated by 11 B-n.m.r. spectroscopy. Three different complexes of myo -inositol have been identified. Formation constants have been determined for the borate complexes of each cyclitol. Where the complex is formed from the less-stable chair conformer, MNDO calculations have been performed to determine the enthalpies of inversion. For myo -inositol, an iterative method of calculation gave a set of constants which provided a good match with experimental data and supported the proposed formulation of its borate complexes.

BORIC ACID COMPLEXES OF PHENOLIC ACIDS

Abstract The complexation between boric acid and the three phenolic carboxylic acids, 3,4-dihydroxybenzoic, caffeic and chlorogenic acids, has been examined spectroscopically and this has established that a 1 : 1 complex is formed in each case. With the first two acids, there is also evidence of a 2 : 1 complex being formed at high acid to B ratios. Equilibrium constants have been calculated from 11 B NMR spectra of mixtures for the equation for the formation of the 1 : 1 complex: B+H 2 A − = BA 2− +H 3 O + . Conditions in which aerial oxidation of the organic acids occurs have been studied by ESR and UV spectroscopy. The presence of boron stabilizes the acids towards oxidation to free radicals and also retards the rate at which the radicals, when formed, are oxidized further to semiquinones.

Electron delocalization in rhodium (1+) bis diisocyanobiphenyl chloride polymers with direct rhodium-rhodium interactions

Abstract It is shown in the present work that hexagonal and tetragonal forms of Rh(I) bis-4,4′-diisocyanobiphenyl chloride polymers containing stacks of rhodium ions in the integral + 1 state show d-electron delocalization in one dimension along Rh+Rh+ chains at and below ambient temperature at atmospheric pressure.

Linear free energy relationships in the thiophene series. Part 3. A kinetic study of chlorine-isotopic exchange between lithium chloride and some 2-chloro-3-nitro-5-X-thiophenes

The rate constants for the chlorine-isotopic exchange between lithium chloride-36 and some 2-chloro-3-nitro-5-X-thiophenes (la—g) have been measured in sulpholane solution. The results obtained give a good Hammett correlation (in the range 323–373 K; calculated ρ 5.55—4.68), indicating that the charge developed in the transition state is strongly affected by the electronic effects of substituents. In order to study the effect of solvent on reactivity, the rates of 2-chloro-3,5-dinitrothiophene (lg) have also been measured in acetone, methanol, and propan-2-ol solutions. A comparison has been made between thiophene and benzene derivatives and the MNDO technique has been used to provide a theoretical model of the exchange reaction.

Experimental and calculated13C chemical shifts for α-, β-, γ- and δ-carbolines

The 13C NMR chemical shifts of the four carbolines 1,2,3,4‐tetrahydro‐β‐carboline, 6,7,8,9‐tetrahydro‐δ‐carboline, 3‐ethyl‐4‐azaindole and 5‐azaindole were assigned from various one‐ and two‐dimensional 1H and 13C NMR spectra. Comparison is made with the results of DFT/GIAO shielding calculations. Copyright

Topochemical solid state [2+2] cyclodimerisations of enones : theoretical considerations

Abstract Molecular orbital calculations using the MNDO computer program were used to study the solid state [2+2] cycloaddition of conjugated enones. Benzylidene methyl ketone was used as a model molecule. The reactive species was identified as a triplet excited state. These calculations were used to clarify the mechanism of this reaction, and to interpret cases of apparent breakdown of the topochemical principle.

Study of the structure and properties of TAPO-5 molecular sieve

The conditions under which some of the Ti4+ ions in TAPO-5 (a titanium containing aluminophosphate) can be reduced to Ti3+ whilst leaving the crystal and pore structure of the molecular sieve intact, have been studied. ESR spectroscopy was used to probe the local geometry round the Ti3+, and was found that this was in a distorted octahedral coordination. The heteroatom was therefore present in a separate microphase locate inside the micropores, in particles too small to be detectable by X-ray diffraction. Two titanium sites were identified. It was found that reduction of Ti4+ involved the lattice oxygens, whilst on exposure to air Ti3+ was oxidised via an electron-transfer mechanism which resulted in the formation of a Superoxide.

Interaction of tin (IV) chloride with sulfolane and between tin (IV) chloride and lithium chloride in sulfolane solution

Tin (IV) chloride reacts with sulfolane (S) to form a cis-octahedral adduct SnCl4·S2. Solutions of lithium chloride and tin (IV) chloride in sulfolane contain the complex ions SnCl5− and SnCl62− at 1∶1 and 2∶1 mole ratios of constituents, respectively. The complexes are characterized by conductimetry and by Mössbauer, IR, and Raman spectroscopy.