Die Reaktion von Tellurhexafluorid mit Trimethylamin,Strukturen der TeF5−- und SeF5−-Anionen

Reaction of Telluriumhexafluoride and Trimethylamine, Structures of the TeF₅^? and SeF₅^? Anions The reaction of TeF₆ and (CH₃)₃N is of the redox kind, resulting in reduction of tellurium: X-ray single crystal analysis reveals the compounds (CH₃)₂N? CH₂? N(CH₃)₂⁺TeF₅^? and [(CH₃)₃NH⁺]₅(TeF₅^?)₃(HF₂^?)₂. By comparison with published data it can be shown that this mixture is identical to previously published [(CH₃)₃N]₂TeF₆. The latter was supposed to be one of the few examples of tellurium in a coordination state of eight. (CH₃)₄N⁺TeF₅^? and (CH₃)₄N⁴SeF₅^? are obtained and their structure is investigated by single crystal x-ray methods also. The anions SF₅^?, SeF₅^? and TeF₅^? are discussed in terms of weak interactions.     

Synthesis and Characterization of Diphenyltin(IV) Dicarboxylates Containing Germanium

Twelve new germanium substituted diphenyltin dipropionates with the general formula (R¹GeCHR²‐CHR³COO)₂SnPh₂ where R¹ = N(CH₂CH₂O)₃, (C₆H₅)₃ and (CH₃C₆H₄)₃, R² = H, CH₃, C₆H₅, p‐CH₃C₆H₄, p‐CH₃OC₆H₄, p‐ClC₆H₄, and R³ = H, CH₃ have been synthesized by the reaction of diphenyltin oxide with a germanium substituted propionic acid. All the compounds were characterized by elemental analysis, IR, multi‐nuclear (¹H, ¹³C, ¹¹⁹Sn) NMR and Mössbauer spectroscopies as well as mass spectrometry. The in vitro antibacterial activity of selected compounds is also reported.     

A novel one-pot synthesis of some new interesting pyrrole derivatives

[reaction: see text] 11-(1H-Pyrrol-1-yl)-11H-indeno[1,2-b]quinoxaline and 3-(1H-pyrrol-1-yl)indolin-2-one derivatives have been synthesized in good yields in a novel, one-pot, and efficient process by condensation of 11H-indeno[1,2-b]quinoxalin-11-one or isatin derivatives with 4-hydroxyproline on solid-support montmorillonite K10 under microwave irradiation.     

Preconcentration and Determination of Chromium Species Using Octadecyl Silica Membrane Disks and Flame Atomic Absorption Spectrometry

A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L^?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples.     

Kinetic studies on the electron transfer between sulphur(IV) and an iron(III) oxime–imine complex

Electron transfer between [Fe^III(L²)]⁺ and sulphur(IV) has been proposed to proceed via an inner-sphere mechanism involving formation of a transient hydrogen-bonded intermediate between the acidic proton of SO₂ · xH₂O/HSO₃ ^– and the oximato oxygen of the coordinated ligand, providing the ready availability of the proton for the reduced complex. In the case of SO₃ ^2–, this is not possible and the reaction is believed to proceed via an outer-sphere scheme.     

Kinetic-spectrophotometric determination of palladium in hydrogenation catalyst by its catalytic effect on the oxidation of pyrogallol red by hydrogen peroxide

A new kinetic-spectrophotometric method is described for the determination of ultra trace amounts of Pd(II). The methods based on catalytic action of Pd(II) on the oxidation of pyrogallol red (PGR) with hydrogen peroxide at pH 9.7. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of the PGR at 540 nm, for the first 4.5 min from initiation of the reaction. Calibration curve was linear in the range of 0.02-1.00 microg ml(-1) Pd(II). The limit of detection is 0.017 microg ml(-1) Pd(II). The relative standard deviation (R.S.D.) for ten replicate analyses of 0.03 and 0.60 microg ml(-1) Pd(II) was 1.5 and 0.9%, respectively. The influence of more than 40 potential interfering ions was studied for the selectivity. The proposed method was used for the determination of palladium in catalytic material.     

Ab initio simulation of benzene Raman intensities

C₆H₆ Raman scattering activities calculated from harmonic model ab initio Hartree–Fock 6–311 ++ G(d, p) polarizability derivatives (and harmonic force fields calculated at the same level) accurately simulate experiment (to within 1% for the a_1g modes). Accurate predictions are also made for the e_2g modes (to within 5% for ν₇ and ν₉, and more poorly for ν₆ and ν₈ [in Fermi resonance with ν₆ + ν₁]) and for the e_1g out-of-plane mode, ν₁₀. Only the ν₆ in-plane CCC bending mode scattering activity is found to be anomalous. Systematic variation of the basis set indicates that the benzene scattering activities and depolarization ratios are strongly dependent on inclusion of both carbon and hydrogen atom diffuse functions in the basis set. Predictions are also made for ¹²C₆D₆ and for unmeasured intensities in ¹³C₆H₆. Measurements of a_1g mode scattering activities in the latter molecule are predicted to be useful in testing the harmonic Hartree–Fock Raman intensity model.     

Spectroscopic and thermodynamic studies on solvatochromic nickel(II) complexes

Summary The solvatochromic and thermochromic behaviour of a series of mixed Ni(II) complexes with unsubstituted and substituted -diketones and diamines in the solvents 1,2-dichloroethane (DCE), acetonitrile (An), acetone (AC),n-butanol (n-BuOH), formamide (FA), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO) and pyridine (PY) has been studied and characterized on the basis of electronic spectra. Spectrophotometric methods have been used to evaluate equilibrium constants and their enthalpic and entropic terms for the formation of Ni(-dik)(diam)L ⁺ and Ni(-dik)(diam)L ₂ ⁺ . Increasing donor strength of the donor-solvents (L) and (or) increasing electronwithdrawing parameters of the substituents at the -diketone and the diamine ligands lead to increasing formation constants, paralleled by relative increase in the stability of the five-coordinated species Ni(-dik)(diam)L ⁺. The results are discussed in terms of the extended donor-acceptor concept.On leave of absence from the Faculty of Education, Ain Schams University, Roxy, Cairo, Egypt     

Determination of trace amounts of cadmium and copper by atomic absorption spectrometry after simultaneous extraction and preconcentration using a new water-soluble polyacrylic acid/alumina sorbent

An analytical method using alumina modified with water-soluble polyacrylic acid polymer for the simultaneous separation and preconcentration of trace Cu and Cd in a column system, and their determination by flame atomic absorption spectrometry was developed. The conditions for coating Al₂O₃ with polyacrylic acid were optimized, then the column was packed with 50 mg of this sorbent. Cd and Cu solution was passed through a glass column at pH 4.5, and elution was carried out with 5 mL of 0.05 M HCl at a flow rate of 1 mL min⁻¹. A sorption capacity of 10 mg Cu and 12 mg Cd was obtained for 1 g sorbent. The detection limit was calculated as 4.5 μg L⁻¹ for Cu and 1.54 μg L⁻¹ for Cd in the final solution. Enrichment factors of 300 for Cd and 400 for Cu were obtained.