Chelate von β-dicarbonylverbindungen und ihren derivaten—teil XLIV. Die extraktion von silber,gold, palladium und platin mit thiodibenzoylmethan1

The extraction of silver(I), gold(III), palladium(II) and platinum(IV) with thiodibenzoylmethane is reported, and methods for the extraction—photometric determination of silver and palladium in trace concentrations are described. Addition of EDTA allows a satisfactory selectivity to be achieved. The influence of foreign metals and complexing agents is discussed.     

Feasible Interior Methods Using Slacks for Nonlinear Optimization

A slack-based feasible interior point method is described which can be derived as a modification of infeasible methods. The modification is minor for most line search methods, but trust region methods require special attention. It is shown how the Cauchy point, which is often computed in trust region methods, must be modified so that the feasible method is effective for problems containing both equality and inequality constraints. The relationship between slack-based methods and traditional feasible methods is discussed. Numerical results using the KNITRO package show the relative performance of feasible versus infeasible interior point methods.     

Intercalation of Toluidines into α-Zirconium Hydrogenphosphate

Intercalates of o-, m-, and p-toluidine into α-Zr(HPO₄)₂ · H₂O were prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. As follows from IR, toludine molecules are protonated in the interlayer space. Toluidine molecules are arranged in a bimolecular way in the intercalates containing more than 1.5 toluidine molecules per Zr atom. On the other hand, a monolayer of the toluidine molecules is supposed in the intercalates with less than one toluidine molecule per Zr atom.     

Ab initioSCF MO calculations on the reactions of hydroxyl radical with imidazole and monoprotonated imidazole

The addition reactions of hydroxyl radical with imidazole and its protonated form to yield radical adducts have been investigated by ab initio SCF MO methods using STO -3G and 4-31G basis sets. Analogous radical species are of importance in radiation damage to biological systems. Of the possible radical products, the calculations indicate that the allylic species are generally favored energetically over the nonallylic forms. On an energetic basis, the results show that the allylic adducts formed by addition at the C2 and C5 positions are about equally favorable. Although the C5 species is generally identified as the experimentally observed product in aqueous media for both protonated and unprotonated imidazole, some experimental evidence exists indicating the presence of other forms. Our results suggest that this other form is the C2 adduct. The calculations also point to the protonated form of imidazole being less reactive than imidazole, which is in accord with experimental observations.     

Calculation of molecular electric polarizabilities and dipole moments. III. BH molecule

We use a previously proposed variation-perturbation method to calculate the electric polarizabilities and the electric dipole moment at equilibrium nuclear distance of the BH molecule. We obtain 3.56 × 10^?24 cm³ for the perpendicular polarizability α_xx and 3.22 × 10^?24 cm³ for the parallel polarizability α_zz. Our result for the electric dipole moment μ₀ is 1.734 debye units; there is no reliable experimental result to compare it with.     

Synthese,Struktur und Reaktivität eines 2,4-Diphosphino-1,3-diphospha-2,4-disilacyclobutans

Synthesis, Structure, and Reactivity of a 1,3-Diphosphino-2,4-diphospha-1,3-disilacyclobutane Pentamethylcyclopentadienyltrichlorosilane reacts with Li[Al(PH₂)₄] to give the stable 1,3-diphosphino-2,4-diphospha-1,3-disilacyclobutane 4 . Treatment of 4 with Lithium alkyls affords the Lithium phosphide 5 via regiospecific metalation of a ring phosphorus atom, and reaction with t-Bu₂Hg proceeds via oxidative P? P bond formation to yield the 1,4-disila-2,3,5,6-tetraphospha-bicyclo[2,1,1]-hexane 6 . Cleavage of pentamethylcyclopentadiene is observed during thermolysis of 4 at 200°C. 4–6 were characterised by NMR-spectroscopy, and 4 by an additional crystal structure determination.