Stabilization of cobalt(II) chloro-complexes with the butanediammonium cation

Summary Cobalt(II) chlorocomplexes with empirical formulae (bnH₂)₂CoCl₆·2H₂O (1) and (bnH₂)₂CoCl₆ (2), where bnH ₂ ²⁺ represents the diprotonated species of putrescine (1,4-butanediamine), were prepared.The visible spectra in the solid state and measurement of the magnetic moments permit the assignation of an octahedral geometry for cobalt in (1) and a tetrahedral geometry for (2).     

Heterogeneous oxidation of pyrimidine and alkyl thioethers in ionic liquids over mesoporous Ti or Ti/Ge catalysts

Heterogeneous catalytic oxidation of a series of thioethers (2-thiomethylpyrimidine, 2-thiomethyl-4,6-dimethyl-pyrimidine, 2-thiobenzylpyrimidine, 2-thiobenzyl-4,6-dimethylpyrimidine, thioanisole, and n-heptyl methyl sulfide) was performed in ionic liquids by using MCM-41 and UVM-type mesoporous catalysts containing Ti, or Ti and Ge. A range of triflate, tetrafluoroborate, trifluoroacetate, lactate and bis(trifluoromethanesulfonyl)imide-based ionic liquids were used. The oxidations were carried out by using anhydrous hydrogen peroxide or the urea-hydrogen peroxide adduct and showed that ionic liquids are very effective solvents, achieving greater reactivity and selectivity than reactions performed in dioxane. The effects of halide and acid impurities on the reactions were also investigated. Recycling experiments on catalysts were carried out in order to evaluate Ti leaching and its effect on activity and selectivity.     

Kinetic study in water-ethylene glycol cationic, zwitterionic, nonionic, and anionic micellar solutions

The spontaneous hydrolysis of phenyl chloroformate was studied in water-ethylene glycol, EG, cationic, zwitterionic, nonionic, and anionic micellar solutions, the surfactants being tetradecyltrimethylammonium bromide, tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, tricosaoxyethylene glycol ether, and sodium dodecyl sulfate. The dependence of the observed rate constant on surfactant concentration as well as on the percentage by weight of EG, varying from 0 to 50 wt %, was investigated. Information about changes in the critical micelle concentrations, in the micellar ionization degrees (for ionic surfactants), in the aggregation numbers, and in the polarity of the interfacial region of the micelles upon changing the weight percent of EG was obtained through conductivity, surface tension, spectroscopic, and fluorescence measurements. A simple pseudophase model was adequate to rationalize the kinetic data. Micellar medium effects were explained by considering charge-charge interactions and polarity, ionic strength, and water content in the micellar interfacial region. The acceleration of the reaction produced by an increase in the amount of EG present in the mixture was explained on the basis of the substantial decrease in the equilibrium binding constant of phenyl chloroformate molecules to the micelles, resulting in the contribution of the reaction taking place in the bulk water-EG phase being more important. The weight percent of EG did not substantially influence the rate constant in the micellar pseudophase.     

Synthesis of octahydroquinolines through the Lewis acid catalyzed reaction of vinyl allenes and imines

The reaction of vinyl allenes with imines under Lewis acid catalysis has been explored. Vinyl allenes in which the allenic portion of the molecule is tri- or tetrasubstituted gave octahydroquinoline derivatives as single isomers together with a minor compound formed by an ene reaction of the imine with the allene. Compounds in which the allene is 1,3-disubstituted do not react under the conditions assayed.     

KMo5O13 and KNb1.76Sb3.24O13

The title compounds, potassium pentamolybdenum oxide, KMo₅O₁₃, and potassium niobate antimonate or potassium niobium antimony oxide (1/1.76/3.24), KNb_1.76Sb_3.24O₁₃, were synthesized by solid‐state reactions and are isomorphous in space group Cmcm. The structure of the Mo complex has three unique Mo atoms and consists of MoO₆ octahedra sharing edges to form Mo₂O₆ pairs and Mo₃O₉ triplets, which, in turn, form layers by sharing corners. These layers are linked together in the [100] direction, yielding a three‐dimensional network similar to that of KSb₅O₁₃. This framework delimits interconnected tunnels, running approximately along the [110] and [10] directions, in which K⁺ ions are located. In the isomorphous KNb_1.76Sb_3.24O₁₃ structure, one of the Mo sites in KMo₅O₁₃ is replaced by Sb and the other two Mo sites have been replaced by Nb/Sb.     

Reactions of thiosemicarbazones derived from beta-keto amides and beta-keto esters with Zn(II) and Cd(II) acetates: influence of metal, substitution, reagent ratio and temperature on metal-induced cyclization

Zinc(II) and cadmium(II) acetates were reacted in methanol under various experimental conditions with thiosemicarbazones derived from beta-keto amides or beta-keto esters (HTSC). Some of these reactions afforded thiosemicarbazonate complexes [M(TSC)2] with IR and NMR spectra compatible with N,S-coordination, but most gave complexes [ML2], where HL is a substituted 2,5-dihydro-5-oxo-1H-pyrazole-1-carbothioamide resulting from cyclization of the HTSC. Some of these pyrazolonates and two of the HL ligands were studied by X-ray diffractometry, and their structures are discussed. Surprisingly, the reactions of zinc(II) acetate with HTSC in 1:1 mol ratio usually gave a third, previously unreported type of complex with a dideprotonated ligand, [Zn(L-H)], which was also formed when [ZnL2] and Zn(OAc)2 interacted at room temperature in 1:1 mol ratio. These L-H complexes are highly insoluble in all common solvents, which hinders their characterization but suggests that they are polymeric in nature.