Determination of As,Sb and Bi in high-purity copper by electrothermal atomic absorption spectrometry

As, Sb and Bi were determined in copper electric cables by atomic absorption spectrometry with electrothermal atomization in a graphite furnace. The interferences in the determination of As, Sb and Bi caused by eleven cationic species and six types of acid were studied. The different volatilization of the copper matrix in comparison to the analyte was studied, as a means of increasing the analyte signal/non-specific absorption signal ratio.     

Fluoride-promoted oxidation of Fischer alkoxy carbene complexes: stoichiometric and catalytic conditions

The utility of fluoride anion as promoter of the oxidation of Fischer carbene complexes is presented. Two different and complementary methods that allow the fast and convenient preparation of carbene-derived esters in good yields have been developed using stoichiometric or catalytic quantities of fluoride ion.     

Syntheses and properties of cyanamide and cyanoguanidine complexes of platinum(II). X-Ray structure of trans-[Pt(CF3)(NCNEt2)(PPh3)2][BF4]

Complexes trans-[PtX(L)(PPh₃)₂]A [1: X = CF₃; A = BF₄; L = NCNH₂, NCNMe₂, NCNEt₂, or NCNC(NH₂)₂. 2: X = Cl; A = BPh₄; L = NCNMe₂ or NCNEt₂] and cis-[PtCl(L)(PPh₃)₂][BPh₄] [3: L = NCNH₂ or NCNC(NH₂)₂], which appear to be the first cyanamide or cyanoguanidine complexes of platinum to be reported, have been prepared by treatment of trans-[PtBr(CF₃)(PPh₃)₂] (in CH₂Cl₂/acetone and in the presence of Ag[BF₄]) or of cis-[PtCl₂(PPh₃)₂] (in THF and in the presence of Na[BPh₄]), respectively, with the appropriate substrate. In KBr pellets or in solution 1 (L = NCNMe₂ or NCNEt₂) undergoes ready replacement of the organocyanamide (under the trans influence of CF₃) by bromide to regenerate trans-(PtBr(CF₃)(PPh₃)₂]. The X-ray structure of 1 (X = CF₃, A = BF₄, L = NCNEt₂) is also reported, and shows the presence of two apical intramolecular contacts of the metal with two ortho-hydrogen atoms of the phosphines, whereas the amine N atom of the diethylcyanamide is trigonal planar in the linear NCN framework with a delocalized π system.     

Copper oxide on Cu/Al2O3-TiO2 catalystsTG,FTIR-CO absorption and catalytic activity in the NO reduction by CO

TG, FTIR-(CO absorption), and catalytic activity in the NO reduction by CO were used to characterize Cu/Al₂O₃-TiO₂ catalysts prepared by co-gelling aluminum tri-sec-butoxide and titanium iso-propoxide at pH 9 and at pH 3 gelling conditions. Under nitrogen flow, copper oxide decomposition, oxygen storage capacity (OSC) and sample dehydroxylation (total mass loss) was followed by TG. The CuO decomposition forming Cu⁰, Cu⁺¹ was observed by means of FTIR (CO absorption) spectra. In pH 9 sample the large amount of Cu⁰ was observed. At low total mass loss and high Cu⁰/Cu⁺¹+Cu⁺² ratio (pH 9 sample) a lowest light-off in the NO reduction by CO was observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The influence of solvent polarity and viscosity on fluorescence of quinolizinium salts

The effects of dielectric constant, viscosity and polarity of the solvents used on the relative fluorescent emission of 2,3-diphenylquinolizinium bromide and 2(p-dimethyl-amino)styryl-3-methylquinolizinium bromide are described. These salts were entirely dissolved in ten different solvents. The 2(p-dimethylamino)styryl derivative produced different ionic species, and was a fluorescent acid-base indicator. The fluorescence of these quinolizinium salts is shown to increase with greater viscosity of the medium.     

Silver polymolybdates and polytungstates as cathodes in lithium-organic solvent batteries

The behaviour of positive electrodes based on silver polymolybdate (Ag₂Mo₂O₇, Ag₆Mo₁₀O₃₃) and polytungstates (Ag₂W₂O₇, Ag₂W₄O₁₃) in lithium-organic solvent batteries has been investigated. The performances of the lithium/silver oxosalt couples are given and the discharge processes are discussed.     

Steric and electronic tuning of chiral bis(oxazoline) ligands with 3,3'-bithiophene backbone

[structure: see text] The role played by the electronic properties and the steric features of bis(oxazoline) ligands in the Cu(I)-catalyzed cyclopropanation of styrene effected with ethyl diazoacetate was investigated. Two pairs of new bis(oxazolines) displaying flexible and atropisomeric 3,3'-bithiophene backbones were synthesized and structurally and electronically characterized. For the first time, the electrochemical oxidative potential was used as a reliable index of the electronic density on the nitrogen atom of the chelating groups of new and, for comparative purposes, of already known bis(oxazolines). The Cu(I) complexes of the new ligands were prepared, and their enantioselection ability and catalytic efficiency were tested. This investigation suggests that steric factors and catalyst geometrical features are clearly more important than any consideration of the electronic properties of the chiral ligands.     

A comparative study of species N3 and P3

Calculations on linear and bent structures of N₃ and P₃ show that these species are quite different. N₃ is linear, P₃ is bent almost to a D_3h geometry. The symmetry of P₃ in D_3h is ²E″ but the Jahn-Teller distortion is very small, ≈4°. The many-body expansion of the energy of P_n clusters appears to be only slowly convergent.     

Bis(triphenylphosphine)4-fluorobenzaldehyde thiosemicarbazone copper(I): Forcing chelation through oxoanions

This paper reports the synthesis and characterization of six compounds of copper(I), stabilized in its reduced state by two triphenylphosphines, in which 4-fluorobenzaldehyde thiosemicarbazone and N-methylthiosemicarbazone act as chelating through their sulfur and imino nitrogen. The three oxoanions that have been chosen, NO₃⁻, SO₄²⁻ and CH₃COO⁻, play an important role: their oxygens are bad competitors with the imino nitrogen of the thiosemicarbazone moiety and moreover they form strong charge assisted hydrogen bondings that stabilize the neutral form of the ligand. The overall packing is determined by intermolecular phenyl–phenyl van der Waals interactions.