Spectrophotometric extractive determination of Ti in mineral samples and aluminium alloys as a mixed-ligand Ti(IV)-salicylhydroxamic acid-thiocyanate complex

A sensitive method for the determination of titanium, based on the formation of a mixed-ligand Ti (IV)-salicylhydroxamic acid-thiocyanate complex and extraction of this into a liquid ion-exchanger phase has been developed. The extract has maximum absorbance at 400–460 nm and the apparent molar absorptivity is 1.8 × 10⁴l · mole^–1 · cm^–1 at 420 nm. The system obeys Beer's law at 420 nm in the range 0.16–3.20 mg/1 Ti, the detection limit being 0.1 mg/1. The method is found suitable for determination of titanium in aluminium alloys and silicate rocks.     

Surface characteristics of titanium–silver alloys in artificial saliva

Titanium and its alloys are widely used in biomedical and dental fields because of their excellent corrosion resistance and biocompatibility. It is well known that titanium is protected from corrosion because of the stability of the passive film that controls and determines the corrosion resistance and biocompatibility of titanium and its alloys. The purpose of this study was to evaluate the electrochemical properties of titanium–silver alloys and the surface characteristics of passive film in artificial saliva. We designed titanium–silver alloys with silver contents ranging from 0 to 5 at.%, in 1% increments. These alloys were arc‐melted, homogenized, hot‐rolled to 2 mm thickness, and finally solution heat‐treated for 1 h and quenched. Potentiostatic testing was performed, and the open circuit potentials of the alloys were measured in artificial saliva, at 37 °C. The passive films of the titanium–silver alloys were analyzed via XPS. Titanium–silver alloys maintained low current density and showed stable passive region and also had high open circuit potential as compared with pure titanium. The open circuit potential of titanium–silver alloys increased as silver addition increased. With regard to the fraction of oxygen species, a component of over 80% was found to be comprised of oxide. Therefore, the titanium surface mainly consisted of titanium oxide and, on the titanium–silver alloys, this film was composed of TiO₂, Ti₂O₃, and TiO. As silver content increased, the TiO₂ fraction also increased, as did the thickness of the titanium oxide layer formed. Copyright © 2005 John Wiley & Sons, Ltd.     

Tris(2-ethylhexyl)phosphate as an extractant for quadrivalent tin,with subsequent determination with pyrocatechol violet in alloy samples

The solvent extraction of tin(IV) from chloride media withtris(2-ethylhexyl)phosphate is presented. Tin(IV) is extracted quantitatively from 2.75–3.20 mol dm^–3 hydrochloric acid using 6.38–6.91 mol dm^–3 tris(2-ethyl-hexyl)phosphate dissolved in toluene as an extractant. After back-extraction of tin(IV) with water from thetris(2-ethylhexyl)phosphate phase, it is estimated spectrophotometrically following complexation with pyrocatechol violet. The recommended range for determination of tin(IV) is 10–100 g. The probable extracted species is SnCl₄·2TEHP. The method is applicable to the analysis of alloy samples with a detection limit of 0.4 g/ml (for 10 g of tin) and a relative standard deviation between 0.21–0.32%.     

Comparative study of magnesium nitrate,palladium nitrate and reduced palladium for the direct determination of mercury in sea water by electrothermal atomization atomic absorption spectrometry

A comparative study of different chemical modifiers in graphite furnace atomic absorption spectrometry for the direct determination of mercury in sea water samples, in synthetic sea water sample of high (72.8%) and low 34.2%) salinity and in aqueous solutions, was carried out. The use of reduced palladium produces better results. The mixture of palladium nitrate and ascorbic acid, gives the best limit of detection (1.9 gl^–1). The use of reduced palladium and magnesium nitrate produced excellent recoveries (close to 100%) in the whole salinity range for all mercury concentration tested. The use of palladium nitrate alone or combined with magnesium nitrate gave good recoveries with respect to a real sea water sample for low salinities. The interference from the major components of sea water were completely removed by using reduced palladium and magnesium nitrate modifiers. Thus, a single calibration curve with synthetic sea water may be applied to the analysis of sea water samples of widely differing salinities.     

Eine weitere Oxovanadat-Phase mit Granatstruktur: Ca5Mg3ZnV6O24

An Additional Oxovanadate Phase with Garnet Structure: Ca₅Mg₃ZnV₆O₂₄ Single crystals of Ca₅Mg₃ZnV₆O₂₄ were prepared by solid state reactions some degree below the melting point of the reaction mixture. It crystallizes with cubic symmetry, space group T-I4 3 d with a = 12.429 Å, Z = 4. The crystal structure is nearly related to the Garnet structure showing Ca²⁺ within distorted cubes (C.N. = 8) of O^2? on a partly unfilled position. the octahedra position are occupied by Mg²⁺ and Zn²⁺ statistically.     

Highly functionalized organomagnesium reagents prepared through halogen-metal exchange

Organomagnesium reagents occupy a central position in synthetic organic and organometallic chemistry. Recently, the halogen-magnesium exchange has considerably extended the range of functionalized Grignard reagents available for synthetic purposes. Functional groups such as esters, nitriles, iodides, imines, or even nitro groups can be present in a wide range of aromatic and heterocyclic organomagnesium reagents. Also various highly functionalized alkenyl magnesium species can be prepared. These recent developments as well as new applications of organomagnesium reagents in cross-coupling reactions and amination reactions will be covered in this Review.     

The crystal structure of a magnesium(II) ethyl diglyme complex

Dibromo[1,1-oxybix[2-ethoxyethane]-O,O,O]-(tetrahydrofuran-O) magnesium, C₁₂H₂₆O₄MgBr₂, crystallizes in space group Pbca witha=7.402(1),b=16.726(2),c=29.248(3) Å,V=3620.9(12) ų,Z=8. The structure was refined toR=0.083 andR _w =0.055 for 1880 observed reflections. Magnesium is octahedrally coordinated by twocis bromine atoms and four oxygen atoms, three from the meridional ethyl diglyme and one from tetrahydrofuran. The Mg–Br distances are 2.614(3)trans to thf and 2.529(3) Åtrans to the central O of the diglyme. The Br–Mg–Br angle is 97.9(1)° and the Mg–O(thf) distance is 2.196(6) Å. The O–Mg–O bite angles subtended by the diglyme are 75.3(2) and 75.7(2)°. The Mg–O(ethyl diglyme) distances are 2.127(6), 2.136(6), and 2.090(6) Å.     

Synthesis of a Hexameric Magnesium 4-pyridyl Complex with Cyclohexane-like Ring Structure via Reductive C-N Activation

The reaction of [{(^Arnacnac)Mg}₂] (^Arnacnac = HC{MeC(NAr)}₂, Ar = 2,6-diisopropylphenyl, Dip, or 2,6-diethylphenyl, Dep) with 4-dimethylaminopyridine (DMAP) at elevated temperatures afforded the hexameric magnesium 4-pyridyl complex [{(^Arnacnac)Mg(4-C₅H₄N)}₆] via reductive cleavage of the DMAP C-N bond. The title compound contains a large s-block organometallic cyclohexane-like ring structure comprising tetrahedral (^Arnacnac)Mg nodes and linked by linear 4-pyridyl bridging ligands, and the structure is compared with other ring systems. [(^Dipnacnac)Mg(DMAP)(NMe₂)] was structurally characterised as a by-product.     

Polymerization of propene with the XTiCl3/MgCl2–Al(i-Bu)3 catalyst system (X = cyclopentadienyl,pentamethylcyclopentadienyl, indenyl,and heptamethylindenyl) in the absence and presence of a lewis base

Several kinds of MgCl₂-supported half titanocene (XTiCl₃; X = cyclopentadienyl, pentamethylcyclopentadienyl, indenyl, and heptamethylindenyl) catalysts were prepared and applied to propene polymerization using Al(i-Bu)₃a as cocatalyst. It was confirmed from the catalyst analysis that the ligand (X) is attached to titanium even after the reaction with Al(i-Bu)₃. When polymerization was conducted without any external donor, those catalysts predominantly gave atactic PP. However, addition of a suitable monofunctional Lewis base like ethylbenzoate caused to change the stereospecificity of polymer from aspecific into highly isospecific. On the other hand, the use of a bifunctional donor like di-n-butylphthalate killed the activity almost completely. The isotactic PP was found to have a microstructure similar to that obtained with metallocene catalysts. © 1997 John Wiley & Sons, Inc.     

Das Kupfer(II)-oxidphosphat Cu4O(PO4)2 in einer neuen,orthorhombischen Modifikation durch Oxidation einer Tl/Cu/P-Legierung

The Copper(II) Oxide Phosphate Cu₄O(PO₄)₂ in a New, Orthorhombic Modification by Oxidation of a Tl/Cu/P Alloy Single crystals of Cu₄O(PO₄)₂ in a new, orthorhombic modification were prepared by reaction of a Tl/Cu/P alloy with oxygen. The compound crystallizes in the space group Pnma with Z = 4 and lattice constants a = 808.8(5) pm, b = 627.0(7) pm, c = 1338.3(1) pm. It is isotypic with the orthorhombic form of Cu₄O(AsO₄)₂. The copper atoms are five-coordinated by oxygen. The distorted square-pyramidal and trigonal-bipyramidal polyhedra are connected by edges and vertices to form [Cu₈O₁₈] ribbons running along [010] and forming slabs perpendicular to the c-axis interconnected by phosphate groups.