Crystal and molecular structure of the triphenylphosphine oxide adduct of tri-3-thienyltin bromide, Ph3 PO·SnBr(C4 H3S)3

The solid state structure of the triphenylphosphine oxide (TPPO) adduct of tri-3-thienyltin bromide has been investigated by both single crystal X-ray analysis and Mössbauer spectroscopy. The crystal structure consists of discrete molecules and there is no evidence of any intermolecular tin-sulphur interactions. Each tin atom is found to be in a five-coordinate trigonal bipyramidal environment in which the three thienyl groups occupy equatorial positions. The metal atom is displaced by 0.182 Å out of the equatorial plane and towards the axial bromine. Two of the thienyl ligands exhibit rotational disorder and the lack of disorder in the remaining heteroaryl ligand is attributed to the close proximity of this group to a phenyl ligand. The Mössbauer parameters are also in accord with five-coordination for tin and are indicative of the aryl groups being equatorial.     

Quantitative ion chromatography with an ultraviolet absorbance detector without standards

Samples of ions are studied by non-suppressed ion chromatography and an ultraviolet absorbance detector. When two eluents of similar properties but different absorptivities per normal concentration are used in succession, two distinct chromatograms are obtained for the same sample. This information can be used to predict the number of equivalents of each ion present, as well as its absorptivity. In conjunction with elution-time studies, molar concentrations can also be obtained. The procedure does not require knowledge of the identity or any physical properties of the ionic species, and is applicable to ions with arbitrary absorption strengths.     

Chemical repercussions of orbital interactions through bond and through space. Effect of remote substituents on the addition of nitrenes to bicyclic olefins

The reactivity of a series of bicyclic olefins with nitrenes is profoundly influenced by the nature of remote functional groups. There is a marked lack of reactivity for reactions with carboethoxynitrene as compared to phthalimidonitrene which is distinctly nucleophilic in character. An explanation for the reluctance to form aziridines is offered in terms of orbital interactions between the distant groups and the olefinic bond, making the latter remarkably electron deficient as evidenced by UV-photoelectron spectrosoopy. Because of the complexity of the spectra, identification of the Ip associated with the reactive π-centre was made by recourse to ab initio configuration interaction calculations for key members of the series.     

The stereochemistry of attack by a carbon electrophile on a tin-carbon bond

In the cyclisation of the 5-stannyl aldehyde (3), the cyclopentanol ring (4) is formed with retention of configuration at the carbon bearing the stannyl group.     

Rapid anisotropic diffusion of lithium in electrochromic thin films based on the hexagonal tungsten bronze structure

The chemical diffusion coefficient of lithium in oxidized potassium hexatungstate and reduced hexagonal potassium tungsten bronze films was measured by the galvanostatic transient method. Two-dimensional anisotropic diffusion was found in the hexagonal hexatungstates, while no appreciable anisotropy was observed in samples with the potassium hexagonal tungsten bronze structure. The chemical diffusion coefficients along the c-axis in thin films of the tungstates K_0.33WO_3.165 and K_0.3WO_3.15 (about 6000 Å thick) are about 10^?10 cm²/s, while those along the a-axis are about 10^?7 cm²/s. This latter value is about the same to those measured in a potassium hexagonal tungsten bronze single crystal of composition K_0.28WO₃ which was grown electrochemically. It is most likely that the presence of the additional oxygen atoms in the tunnels within the hexatungstate structure is responsible for the large decrease in the rate of motion of lithium along the c-axis that leads to the anisotropy in the macroscopic diffusion coefficient in this crystal structure.     

Extending a Gas Pipeline Network

This paper describes the use of a mixed-integer programming model for the problem of determining methods of reinforcing and increasing a natural gas pipeline network. The model considers the options of (i) reinforcing pipes, (ii) building new pipes into the network, (iii) setting up of liquid natural gas tanks at certain points on the network, and attempts to find the best policy for satisfying demand levels. Because of the difficulties of solving the resultant mixed-integer problem, the model can only be used for small networks.