Polyhedral metallaheteroborane chemistry. Synthesis, spectroscopy, structure and dynamics of eleven-vertex {RhNB(9)} and {PtCB(9)} metallaheteroboranes

Reaction between [RhCl(PPh(3))(3)] and the [nido-6-NB(9)H(11)](-) anion in CH(2)Cl(2) yields orange eleven-vertex [8,8-(PPh(3))(2)-nido-8,7-RhNB(9)H(11)]. Reaction of the [nido-6-CB(9)H(12)](-) anion with [cis-PtCl(2)(PMe(2)Ph)(2)] in methanol affords yellow eleven-vertex [9-(OMe)-8,8-(PMe(2)Ph)(2)-nido-8,7-PtCB(9)H(10)], which is also formed from the reaction of MeOH with [8,8-(PPh(3))(2)-nido-8,7-PtCB(9)H(10)]. Both compounds have been characterised by single-crystal X-ray diffraction analysis and examined by NMR spectroscopy and have structures based on eleven-vertex nido-type geometries, with the metal centre and the heteroatoms in the adjacent (8)- and (7)-positions on the pentagonal open face. The metal-to-heteroborane bonding sphere of is fluxional, with a DeltaG(double dagger) value of 48.4 kJ mol(-1). DFT calculations on the model compounds [8,8-(PH(3))(2)-nido-8,7-RhNB(9)H(11)] and [8,8-(PH(3))(2)-nido-8,7-RhSB(9)H(10)] have been carried out to define the fluxional process and the intermediates involved.     

Azatricarbaborane 7-t-Bu-arachno-7,1,5,12-NC3B8H12 and Parent Tricarbaboranes nido-[5,6,9-C3B7H10]- and -5,6,9-C3B7H11

The neutral azatricarbaborane 7-t-Bu-arachno-7,1,5,12-NC(3)B(8)H(12), isolated as a side product (yield 2%) from the new synthesis of 7-t-BuNH2-nido-7,8,9-C(3)B(8)H(10) (yield 70%), can be easily converted to the first parent representatives of the 10-vertex nido family of tricarbaboranes, [5,6,9-C(3)B(7)H(10)]- and 5,6,9-C(3)B(7)H(11).     

Differential pulse voltammetric determination of selected nitrophenols on novel type of porous silver working electrode prepared by powder metallurgy

Nitrophenols are important environmental pollutants and their monitoring is important because of their genotoxic and ecotoxic properties. Easy electrochemical reduction of nitro groups can be used for their voltammetric determination using mercury based electrodes. However, requirements of green analytical chemistry prompted us to investigate a novel type of silver porous electrode (AgPE) prepared by powder metallurgy compatible with both “green” and “white” analytical chemistry requirements. In this paper, AgPE was for the first time successfully used for differential pulse voltammetric determination of micromolar concentrations of 2-nitrophenol (NP), 2,4-dinitrophenol (DNP), and 2,4,6-trinitrophenol (TNP) in aqueous media. The main advantage of the novel method is the possibility to use small sample volume (down to 25 μL) and to work in the presence of oxygen when using supporting electrolyte of pH 3. This advantage partially compensates the fact that the obtained sensitivity and limit of detection are not better than with the previously investigated electrodes.     

Tailoring of polymers by combination of ionic and radical controlled polymerizations

Poly(methyl methacrylate)s with terminal bromine atom, prepared by bromination of anionically polymerized MMA, were used as ATRP macroinitiators giving di- and triblock copolymers with MMA, styrene and butyl acrylate blocks. Multifunctional ATRP macroinitiators were synthesized by introducing bromomethyl or 2-bromoacyloxy groups onto the main chain of polystyrene or poly(4-methyl styrene) and used for ATRP grafting of tert-butyl acrylate leading to densely grafted copolymers with more or less uniform grafts.     

Purity and doping possibilities of Al2O3 and YAG molten in Mo crucibles and crystals grown from this melt

Doping possibilities of Al₂O₃ and YAG crystals grown from the melt alternatively doped with alkali earth, silicon, iron group or molybdenum ions under 98% Ar – 2% H₂ or 98% He – 2% H₂ protective atmosphere are described. Alkali earth and particularly Si ions evaporate slowly from the melt. Reduction of iron group ions was observed. Mo may enter YAG phase using a wet protective atmosphere. Al₂O₃ phase contains Mo ions if grown from the electrolyzed melt.     

Use of the diffusive gradients in thin films technique (DGT) with various diffusive gels for characterization of sewage sludge-contaminated soils

The diffusive gradients in thin film technique (DGT) was used for characterization of South Moravian arable soils (sampling sites Zlín, Tuřany, and Chrlice) amended by sewage sludge in the 1980s. Two types of polyacrylamide diffusive gel with different pore size (APA gels—cross-linked with agarose and RG gels—cross-linked with bis-acrylamide) were employed. The (bio)available parts of Cd, Cu, and Ni and the proportions of inorganically and organically complexed species of these metals were assessed. The degree of metal resupply from the soil solid phase to the soil solution was also determined. Metal concentrations obtained by the DGT technique were lower by almost 4 to 5 orders of magnitude in comparison with those obtained by extraction with aqua regia. DGT concentrations of metals were also lower by approximately 1 to 2 orders of magnitude in comparison with those obtained by extraction with sodium nitrate (commonly used for assessment of the (bio)available part of metals). Results obtained by DGT measurement were expected to be closer to the actual content of available metal species than results obtained by extraction with sodium nitrate. Using RG gels together with APA gels provided resolution of inorganically and organically complexed metal species and their proportional representation. Inorganic metal species (particles smaller than 1 nm) formed a predominant part of assessed metal content in all studied soil samples and horizons. However, there was the exception of the cadmium content in the middle profile of Chrlice sandy soil sample. Ratio R values indicated that resupply of Cd, Cu, and Ni from the solid phase to the soil solution varied for individual soil samples and individual depth profiles. Mobile and labile species of Cd, Cu, and Ni were much more closely related to upper rather than deeper horizons. This observation correlates very well with the mechanical treatment and amendment of the studied soils.     

10<Emphasis Type="Italic">α</Emphasis>-Hydroxy-<Emphasis Type="Italic">β</Emphasis>-isomorphine,a by-product of the synthesis of 10<Emphasis Type="Italic">α</Emphasis>-hydroxymorphine

Abstract  A new compound was isolated from the reaction mixture after O-demethylation of 6-O-acetyl-10α-acetoxycodeine with boron tribromide. The structure of this compound, 10α-hydroxy-β-isomorphine, was elucidated by spectral data, and its spatial arrangement was deduced from an NOE experiment. Capillary zone electrophoresis was used for separation of morphine and its 10-hydroxy analogues. Graphical abstract