The effect of phase composition of Ti-20 at % Cr alloy on its anodic activation in the chloride and bromide solutions

The effect of phase composition of Ti-20 at % Cr alloy on its anodic behavior in the solutions containing aggressive Cl⁻ and Br⁻ anions and, for comparison, non-aggressive SO₄²⁻ anion is studied. Different phase compositions of the alloy were obtained by using different modes of heat treatment. The features of anodic behavior of alloys with various phase compositions are related to the electrochemical properties of titanium and chromium, their tendency to passivation and breakdown of passivity in the presence of various anions.     

Dendritic styryl TADDOLs as novel polymer cross-linkers: First application in an enantioselective Et2Zn addition mediated by a polymer-incorporated titanate. Preliminary communication

TADDOLs (α,α,α′,α′,-tetraaryl-1,3-dioxolane-4,5-dimethanols) with dendritic branches attached to the aryl groups and with 8 or 16 peripheral styryl double bonds have been synthesized ( 4 and 5 ). With these compounds, dendritic molecules were employed for the first time as cross-linkers in a polymerization. The resulting polystyrene was loaded with titanate (Ti(OCHMe₂)₄) to generate polymer beads incorporating Ti-TADDOLate centers (Figs. 1 and 2) for enantioselective catalysis (Et₂Zn addition to PhCHO). Compared with conventionally polymer-attached, insoluble Ti-TADDOLates (cf. 3 ), the new materials have a much higher catalytic activity, rather close to that of soluble analogs (Fig. 3).     

N‐Silylaminotitanium Chlorides — Synthesis,Structures, Multinuclear Magnetic Resonance,and some Applications

N‐Silylaminotitanium trichlorides, Me₃S(R)N‐TiCl₃ ( 18 ) [R = ^tBu ( a ), SiMe₃ ( b ), 9‐borabicyclo[3.3.1]nonyl (9‐BBN)( c )], and (CH₂SiMe₂)₂N‐TiCl₃ ( 18d ) were obtained in high yield and high purity from the reaction of the respective bis(silylamino)plumbylene with an excess of titanium tetrachloride. The crystal structure of 18a was determined by X‐ray analysis. The reactions of the analogous stannylenes with an excess of TiCl₄ did not lead to 18 . N‐Lithio‐trimethylsilyl[9‐(9‐borabicyclo[3.3.1]nonyl)]amine ( 8 ) was prepared, structurally characterized and used for the synthesis of a new bis(amino)stannylene 10 and a plumbylene 11 . The compounds 18a—d served as ideal starting materials for the synthesis of bis(silylamino)titanium dichlorides, where the silylamino groups can be identical ( 19 ) or different ( 20 ). This was achieved either by the reaction of 18 again with bis(amino)plumbylenes or with lithium N‐silylamides. In contrast to the direct synthesis starting from titanium tetrachloride and two equivalents of the respective lithium amide, which in general affords 19 with identical amino groups only in low yield, the procedure starting from 18 is much more versatile and gave the pure compounds 19 or 20 in almost quantitative yield. Further treatment of the dichlorides 19 or 20 with lithium amides led to tris(amino)titanium chlorides 21 . The dichlorides 19 or 20 reacted with two equivalents of alkynyllithium reagents to give the first well characterized examples of di(alkyn‐1‐yl)bis(N‐silylamino)titanium compounds 22 — 27 . These compounds reacted with trialkylboranes (triethyl or tripropylborane) by 1, 1‐organoboration. In some cases, the extremely reactive reaction products could be identified as novel 1, 1‐bis(silylamino)titana‐2, 4‐cyclopentadienes 28 — 31 bearing a dialkylboryl group in 3‐position. In solution, the proposed structures of all products were deduced from a consistent set of data derived from multinuclear magnetic resonance spectroscopy (¹H, ¹¹B, ¹³C, ¹⁴N, ¹⁵N, ²⁹Si, ³⁵Cl NMR).     

Low-voltage thin-layer electrophoresis of inorganic anions on silica gel-G and titanium (IV) tungstate layers: separation of coexisting F−, Cl−, Br− and I−, I−, IO3− and IO4−, Fe(CN)64− and Fe(CN)63−

The electrophoretic behavior of twenty anions has been studied on silica gel-G, titanium (IV) tungstate and silica gel-G- titanium (IV) tungstate admixture layers using 0.1 M solutions of oxalic acid, citric acid, tartaric acid, succinic acid and acetic acid as background electrolyte. The mechanism of migration is explained in terms of adsorption and the solubility of various sodium or potassium salts of the anions in water. Titanium (IV) tungstate behaves only as an adsorbent and not as an ion exchanger. Being a cation exchanger, there is no exchange phenomenon occurring with anions. The migration of halides increase linearly with an increase in the bare ion radii of these ions. Differential migration of the anions on silica gel-G layers led to binary, ternary and quaternary separations of similar anions such as F⁻ – Cl⁻ – Br⁻ – I⁻, I⁻ – IO₃⁻ – IO₄⁻, BrO₃⁻ – IO₃⁻ and Fe(CN)₆³⁻ – Fe(CN)₆⁴⁻. The two cyanoferrate ions are separated from industrial waste water and from fixer and bleach solutions. The migration of anions has also been found to be in accordance with their lyotropic numbers.

     

Emulsion polymerization of styrene. III. Effect of Ti(III) and Cl(1) on the polymerization of styrene initiated by potassium persulfate

The emulsion polymerization of styrene initiated by potassium persulfate catalyzed by Ti⁺³ ions was studied. Two sources of Ti⁺³ ions were used: the titanium trichloride and titanium sulfate. It was found that the titanium ions used in conjunction with potassium persulfate decrease both the reaction rate and the average molecular weight. An even greater drop of reaction rate was noted when chlorine anions (TiCl₃) were present. The presence of these ions had a stabilizing effect on the polydispersity.     

Facile preparation of transparent monolithic titania gels utilizing a chelating ligand and mineral salts

Highly homogeneous transparent titania gels have been successfully prepared from titanium alkoxide by a sol–gel method utilizing chelating agent, ethyl acetylacetate (EtAcAc), in the presence of strong acid anions. Only catalytic amount of a strong acid anion suppress the rapid hydrolysis of titanium alkoxide by blocking the nucleophilic attack of HO⁻ and H₂O, and the resultant moderate sol–gel reactions thus afford homogeneous gelation, leading to transparent monolithic titania gels. Gelation time can be widely controlled by changing amounts of water, chelating agent and salt. The ability of salts to suppress the too abrupt sol–gel reactions is strongly dependent on the electronegativity of anions and valence of cations. With employing NH₄NO₃ as a suppressing electrolyte, the obtained titania gels can be converted to pure TiO₂ by simple washing and heat-treatment, and transformations to anatase and rutile structures were found to start at 400 and 600 °C, respectively.     

Photocatalysis by titanium complexes of the reaction of ClO4 −, ions with alcohol molecules

In the photolysis of perchloric acid solutions of titanium(IV) with additions of ethanol, the formation of titanium(III) compounds was detected. Irradiated solutions ([HClO₄]=0.8 M) at 77K are characterized by an anisotropic ESR signal with parameters g ₁=1.994, g ₁=1.904, which correspond to pseudo-octahedral aqua-complexes of titanium(III). With the passage of time, the signal intensity of the titanium(III) compounds decreases, which is explained by their oxidation by ClO₄ ions. During prolonged photolysis of titanium(IV) compounds in 7 M HClO₄ with an addition of ethanol, a multicomponent signal of the paramagnetic chlorine oxide ClO₂ with parameters g _xx=2,004, a _xx(³⁷Cl)=6.0. mTl a _xx(³⁵Cl)=7,30 mTl, is recorded instead of the signal of titanium(III) compounds. Evidently ClO₂ is formed as a result of a rapid dark reaction between compounds of trivalent titanium (products of the photochemical step) and chlorate ions, which are accumulated in the solution as a result of successive photochemical and dark redox conversions of the titanium compounds, perchlorate ions, arid free radicals from the alcohol molecules. The formation of free radicals in the system was established by the ESR method after irradiation of frozen solutions.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 6, pp. 679–686, November–December, 1986.     

Electrolytic coating of titanium onto iron and nickel electrodes in the molten LiF + NaF + KF eutectic

The electrolytic reduction of Ti(III) species in LiF+NaF+KF eutectic on iron and nickel, studied using voltammetric techniques, proceeds reversibly in the 600–700°C temperature range. No interaction occurs between the iron electrode and the titanium coating, whereas the solubility of titanium in nickel has been proved. Chronoamperometric measurements at constant potentials more positive than the Ti(III)/Ti equilibrium potential indicate that the electrochemical incorporation of titanium in nickel is controlled by intermetallic diffusion.Coatings of pure titanium 20 to 30 μm thick were produced on iron at 700°C and on nickel at 600 and 700°C; they were homogeneous and well-crystallized. X-ray fluorescence analysis showed that the pure titanium coating is joined to the nickel supporting metal by a multilayer zone consisting of Ti₂Ni, TiNi and TiNi₃ definite compounds.     

Tungsten/Alumina Catalysts: Effect of H3PW12O40 Countercation on Surface Properties and Hydrodesulfurization Activity

H₃PW₁₂O₄₀ heteropoly acid (HPW₁₂) and its Co, Fe, Ni salts supported on alumina have been used to model hydrodesulfurization catalysts of different activity. All catalysts revealed a promoting effect of the countercation in thiophene hydrodesulfurization, that of the nickel cation being the highest. The catalysts were characterized by measurements of surface area, HDS activity, TPR, FTIR, and DR spectra. IR spectra confirmed an effect of the countercation on the phase composition of the supported heteropoly compounds. 12-Tungstoaluminate heteropoly anions and coordinately unsaturated anions of HPW₁₂ were detected in the IR spectra of the catalysts. The hydrotreating activity of the catalysts was proportional to the amount of hydrogen consumed in the range 20–500°C during TPR.     

State of titanium in supported titanium-magnesium catalysts for propylene polymerization

The oxidation state of titanium and the coordination state of Ti³⁺ ions in TiCl₄/D₁/MgCl₂ (D₁ is a phthalate) supported titanium-magnesium catalysts (TMCs) after the interaction with an AlEt₃/D₂ cocatalyst (D₂ is propyltrimethoxysilane or dicyclopentyldimethoxysilane) were studied by chemical analysis and EPR spectroscopy. Different oxidation state distributions of titanium ions were observed in the activated catalyst and mother liquor: Ti³⁺ and Ti²⁺ ions were predominant in the activated catalyst and mother liquor, respectively. The effects of interaction conditions (reaction temperature and time and Al/Ti and D₂/Ti molar ratios) of TMCs with the cocatalyst on the state of titanium in activated samples were studied. The interaction of TMCs with the cocatalyst decreased the titanium content and caused the appearance of aluminum in the activated sample, which was most clearly pronounced at a temperature of 25°C and occurred within the first 10 min of treatment. An increase in the temperature to 70°C and an increase in the interaction time to 60 min only slightly affected the concentrations of titanium and aluminum. The presence of D₂ as a cocatalyst constituent facilitated the removal of titanium compounds and restricted the adsorption of aluminum compounds on the catalyst surface. The main fraction of titanium consisted of Ti³⁺ ions (62–89%), and the rest was Ti⁴⁺ ions (22–35%) under mild interaction conditions (25°C; Si/Ti = 25) or Ti⁴⁺ (0–21%) and Ti²⁺ (9–21%) ions under more severe conditions (50 or 70°C; Si/Ti from 0 to 5). According to EPR-spectroscopic data, at D₂/Ti from 1 to 5, Ti³⁺ ions mainly occurred as associates, whereas they occurred as isolated ions at D₂/Ti = 25. The initial and activated catalysts were similar in activity in the reaction of propylene polymerization, and titanium compounds, which were removed from the catalyst upon interaction with AlEt₃/D₂, were inactive in this process.     

Heteroselenometallic cluster compounds with tetraselenometalates

The coordination cluster compounds of tetraselenomolybdate and tetraselenotungstate anions with metal ions are reviewed. New heteroselenometallic cluster compounds are primarily of interest regarding their structures and reactivities, and their potential as non-linear optical (NLO) materials. This article focuses from a synthetic and structural point of view on coordination cluster compounds with tetraseleno-molybdate and -tungstate anions as polydentate ligands. A comprehensive survey is presented of the heteroselenometallic clusters known to date according to the number of center [MSe₄]²⁻ (M=Mo, W) anions. Representative spectroscopic and NLO properties of these clusters are also discussed.     

CpTiCl3-alumina-silica system reduced with NaNp

The system CpTiCl₃/Al₂O₃–SiO₂ (0–100 wt.% of Al₂O₃), (Cp=cyclopentadienyl) was reduced with a tenfold excess of NaNp (Np=naphthalene) in THF and argon atmosphere at room temperature. Only titanium(IV) and titanium(III) compounds were found by the polarographic method in the systems studied. The amount of the titanium(III) compounds is influenced by the acidity of supports.     

Anion Selectivity of Tetravalent Tin Compounds in Membranes Studied by 119Sn-, 13C- and 1H-NMR

The fundamental molecular aspects of trialkyltin compounds of the type R₃SnY have been investigated in view of their applicability as ion-selective components in solvent polymeric membranes. The interaction between these compounds and anions has been studied using ¹¹⁹Sn- and ¹³C-NMR. Neutral tetracoordinated trialkyltin compounds form a negatively charged pentacoordinated complex upon interaction with Cl-ions in homogeneous organic phases as well as in membranes in contact with aqueous solutions. Although in a homogeneous phase, the electronegative substituent Y determines the complex-formation constant, it has no influence on the potentiometric anion selectivity in liquid membranes containing trialkyltin carriers R₃SnY with different Y. The observed selectivity pattern is not given by the magnitude of the stability constants in a homogeneous phase but is dictated by the prevailing association-dissociation process leading to tetracoordinated compounds which change in constitution due to varying sample composition, The results obtained from equilibrium studies of tetravalent mono tin compounds with anions in both homogeneous phase and in two-phase systems confirm the earlier hypothesis that trialkyltin compounds incorporated in solvent polymeric membranes act as electrically neutral carriers for anions.     

Tetrathiafulvalene-based organic conductors with Pb-containing anions

Hybrid compounds containing organic layers composed of tetrathiafulvalenes (BEDT-TTF, BETS, BEDO-TTF) and inorganic layers consisting of anions based on lead bromide were synthesized. The crystal structure of (BEDT-TTF)₆Pb₃Br₁₀(PhBr) was determined. The temperature dependences of electrical conductivity for the synthesized compounds were measured and the EPR spectra of these compounds were recorded. In the structure of (BEDT-TTF)₆Pb₃Br₁₀(PhBr), the organic conducting layers of BEDT-TTF molecules alternate with non-conducting layers composed of infinite chains of bromoplumbate anions [Pb₃Br₉]^3–, solvent molecules, and Br^– anions. The newly synthesized BEDT-TTF bromoplumbates have similar linewidths of EPR signals, which indicate that their conducting layers have similar structures. The BEDT-TTF bromoplumbates are semiconductors, while temperature-dependent electrical resistivity measurements show the metallic behavior for BEDO-TTF and BETS bromoplumbates.     

芳酰基硫脲受体的合成及对阴离子识别研究

设计合成了3种芳酰基硫脲受体分子. 利用紫外-可见吸收光谱考察了其与F^－, Cl^－, Br^－, AcO^－, HSO₄^－, H₂PO₄^－等阴离子的作用. 结果表明该类受体分子与阴离子形成氢键配合物. 加入F^－, AcO^－时, 溶液立刻由无色变为黄色, 而加入其它阴离子则无变化, 从而实现对这两种阴离子的裸眼识别. 结果表明受体分子与阴离子间形成1∶1型的配合物. ¹H NMR滴定及质子溶剂效应为受体分子与阴离子间的氢键作用本质提供了直接依据.     

New anionic species of tellurium(IV)

Tetrahaloaryltellurates(IV) were prepared by refluxing aryltellurium trihalides with phosphonium, tropylium and telluronium halides in CHCl₃. These compounds, which contain the ArTeX^?₄ anion, may be also prepared from aryltellurium trihalides and aqueous halogen hydride solutions. The phosphonium derivatives can be considered as potential precursors of tellurophosphoranes for Wittig reactions. Halogen exchange reactions allow the interconversion of the complex anions. The ionic nature of the compounds is supported by ion exchange reactions utilizing ion exchange resins, and by conductance measurements. Far infrared and Raman spectral data suggest a square pyramidal configuration for the ArTeX^?₄ anions.     

A New Approach for the Determination of Organobromine in Harmful Waste

Determination and estimation of organic sulphur, nitrogen, phosphor and halides in harmful chemical waste and estimation of emission of SO₂, NO_X, HCI, HBr or HI during incineration are the primary task of risk assessment. In our paper we present a new analytical approach for determination of bromine in a heterogeneous sample. The method applied is based on combustion of chemical waste under oxygen atmosphere (pressure 20 bars) and transformation to corresponding anions. These anions can be measured by ion chromatography. Using this method all hetero atoms can be transformed to corresponding anions (except for oxygen) and can be measured by ion chromatography. In this paper we report of determination of bromine content of chemical waste. During the combustion of organobromine compounds different types of inorganic bromine are formed. All types of bromine must be converted to Br^–. To fulfil it the above, ascorbic acid solution was used for absorbing and transforming all types bromine compounds to Br^–. We will discuss all the details about this new approach and give all the parameters to get efficient conversion from organic bromine to bromide anions.This revised version was published online in November 2005 with corrections to the Cover Date.     

Coordination chemistry of 5,6,7-trimethyl-[1,2,4]triazolo[1,5-a]pyrimidine with first-row transition-metal salts: Synthesis, spectroscopy and single-crystal structures, with counter-anion dependence of the structures

A variety of new coordination compounds with transition-metal salts and the ligand trimethyl[1,2,4]triazolo[1,5-a]pyrimidine (abbreviated as tmtp) is described, together with several of their 3D crystal structures and spectroscopic and magnetic properties. The compounds were selected based on the coordination ability of the counterion, halide, nitrate, sulfate, thiocyanate and perchlorate. The formed coordination compounds and their coordination numbers were found to be strongly dependent on both the cation and the used counter-anion. The several compounds studied have the following structural formulae: [CuCl₂(tmtp)₂], [CuBr₂(tmtp)₂], [ZnBr₂(tmtp)₂], [Cu(NO₃)₂(tmtp)₂], [CuSO₄(tmtp)₂]₂(H₂O)(MeOH), [Cu(H₂O)(NCS)₂(tmtp)₂], [Zn(NCS)₂(tmtp)₂], [Cd(NCS)₂(tmtp)₂] and [M(H₂O)₂(tmtp)₄](BF₄)₂, in which M = Co, Ni, Zn.The new coordination compounds have been further characterized by NMR, (far-)IR and LF spectra, as well as by C, H, N element analyses, and EPR spectra for the Cu(II) compounds. The coordination around the metal varies from 4 (Zn, Cu), via 5 (Cu) to 6 (for Co, Cu and Cd). The anions usually complete the coordination sphere; only the Co and Zn compounds with the tetrafluoridoborate anions have no coordinated anions, but water ligands complete the octahedral coordination sphere. In the 5-coordinated [Cu(H₂O)(NCS)₂(tmtp)₂] water completes the square pyramid geometry.     

Yellow pigments based on Fe2TiO5 and TiO2

The aim of our research was to prepare yellow pigments based on structure of pseudobrookite Fe₂TiO₅. Part of Fe was substituted with Li and Ti from Fe₂TiO₅ to Li_0.05Fe_0.07Ti_2.44O₅. Synthesis and pigmentary-application properties in the Li₂O–Fe₂O₃–TiO₂ system were studied for 800 and 900°C using classical ceramic method of preparation. The main attention was aimed to usage of four different sources of titanium compounds as raw materials. We studied the influence of different sources of titanium compounds on the structural and the colour properties of the prepared pigments. The thermal analysis was used for characterization of titanium compounds and determination of their thermal stability.