Theoretical Study of Chemical Binding of Noble Gas Atom and Transition Metal Complexes: Ng–NiCO, Ng–NiN2, Ng–CoCO (Ng = He–Xe)

Summary. Ab initio multireference and coupled cluster methods (MR-SDCI(+Q), CASPT2, CCSD(T)) and density functional theory methods (B3LYP, MPWPW91) have been applied to examine geometrical structures and vibrational frequencies of noble gas (Ng) – transition metal compounds, Ng–NiCO, Ng–NiN₂, and Ng–CoCO (Ng = He, Ne, Ar, Kr, Xe). It is shown that the respective compounds can have a larger binding energy than a typical van der Waals interaction energy. The binding mechanism is explained by a partial electron transfer from a noble gas atom to the low-lying 4s and 3d vacant orbitals of the transition metal atom. Theoretical calculations show that the binding of noble gas atom results in a large shift of the bending frequency: 361.1cm^–1 (NiCO) to 403.5cm^–1 (Ar–NiCO); 308.5cm^–1 (NiN₂) to 354.8cm^–1 (Ar–NiN₂); 373.0cm^–1 (CoCO) to 422.6cm^–1 (Ar–CoCO). The corresponding experimental frequencies determined in solid argon are 409.1cm^–1 (NiCO), 357.0cm^–1 (NiN₂), and 424.9cm^–1 (CoCO), which are much closer to the corresponding frequency of Ar–NiCO, Ar–NiN₂, and Ar–CoCO, respectively.     

Metal Sorption,Solid Phase Extraction and Preconcentration Properties of Two Silica Gel Phases Chemically Modified with 2-Hydroxy-1-Naphthaldehyde

Active silica gel phase (I) was chemically modified to the corresponding amino- (SiNH₂) and chloro- (SiCl) derivatives via silylation reactions. These were used to synthesize two newly modified silica gel phases (II, III) by direct chemical reaction with 2-hydroxynaphthaldehyde (2-HNA). The surface coverage values are 370, 432µmolg^–1 and 320, 355µmolg^–1 for (II) and (III), on the basis of thermal desorption and metal probe testing method, respectively. The metal sorption properties of silica gel phases (II, III) were studied and compared with active silica gel phase (I). The maximum determined metal capacity values were found to be 10–110, 20–290 and 20–370µmolg^–1 for phases I, II and III, respectively. The distribution coefficient values (K_d) were also determined for a series of metal ions, and the results showed that the two new chemically modified phases (II and III) were highly selective for Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺ and Pb²⁺. The potential applications of silica gel phases (II, III) as solid phase extractors for the same five metal ions spiked in drinking tap water (1.000µgmL^–1) were found to give percentage recovery values in the range of 90.2–96.3±4.1–6.3%, while pre-concentration of the same five metal ions spiked in drinking tap water (50.0ngmL^–1) was successfully accomplished with a percentage recovery range of 92.6–95.8±4.8–5.7%.Received December 16, 2002; accepted May 14, 2003 published online September 1, 2003     

Kinetics and mechanism of the interaction of azide with [(H2O)(tap)2RuORu(tap)2-(H2O)]2+ ion at physiological pH

The title reaction has been studied spectrophotometrically in aqueous medium as a function of [substrate complex], [ligand], pH and temperature at constant ionic strength. At the physiological pH (7.4) the interaction with azide shows two distinct consecutive steps, i.e., it shows a non-linear dependence on the concentration of N₃ ^–; both processes are [ligand]-dependent. The rate constant for the processes are: k ₁10^–3 s^–1 and k ₂10^–5 s^–1. The activation parameters calculated from Eyring plots are: H ₁ = 14.8 ± 1 kJ mol^–1, S ₁ = –240 ± 3 J K^–1 mol^–1, H ₂ = 44.0 ± 1.5 kJ mol^–1 and S ₂ = –190 ± 4 J K^–1 mol^–1. Based on the kinetic and activation parameters an associative interchange mechanism is proposed for the interaction process. From the temperature dependence of the outersphere association equilibrium constant, the thermodynamic parameters calculated are: H ₁ ⁰ = 4.4 ± 0.9 kJ mol^–1, S ₁ ⁰ = 64 ± 3 J K^–1 mol^–1 and H ₂ ⁰ = 14.2 ± 2.9 kJ mol^–1, S ₂ ⁰ = 90 ± 9 J K^–1 mol^–1, which gives a negative G ⁰ value at all temperatures studied, supporting the spontaneous formation of an outersphere association complex.     

Pitzer Parameters for the Pertechnetate Ion in the System Na+/K+/Mg2+/Ca2+/Cl−/SO 2 4 −/TcO − 4 /H2O at 25°C

Isopiestic vapor pressure experiments are performed at 25°C with aqueous Mg(TcO₄)₂ solutions and with ternary mixtures containing various combinations of NaTcO₄, Mg(TcO₄)₂, NaCl, MgCl₂, Na₂SO₄, and MgSO₄. The osmotic coefficients of the binary solutions are used to evaluate the binary Pitzer parameters ⁽⁰⁾, ⁽¹⁾, and C for Mg(TcO₄)₂. We previously reported these parameters for NaTcO₄. The binary parameters for KTcO₄ and Ca(TcO₄)₂ are evaluated from solubilities of KTcO₄ in KCl and CaCl₂ solutions, respectively. The mixing parameters _{TcO 4} ^– _/Cl ^–, _{M/TcO 4} ^– _/Cl ^–, _{TcO 4} ^– _{/SO 4} ^2– , _{M/TcO 4} ^– _{/SO 4} ^2– , and _Na ⁺ _/Mg ²⁺ _/TcO4 ^2– are calculated from either osmotic coefficients or solubilities in the corresponding ternary mixtures. The evaluated set of Pitzer parameters predicts well the activity coefficients and solubilities of KTcO₄ in multicomponent systems.     

Reversible sorption of hydrogen by colloidal palladium in aqueous solutions

Colloidal palladium was prepared by -irradiation or by H₂ reduction of Pd(NH₃)₄l₂ in aqueous solutions containing sodium polyacrylate as a stabilizer. The sots contain spherical particles 2–4 nm in diameter. Their optical spectra contain a band at 230 nm ( = 6.1 · 10³ L mol^–1 cm^–1) smoothly descending toward the visible range. The sots reversibly absorb chemically from 0.35 to 0.15 g-mol of H₂ per g-atom of Pd. The spectra of ultrafine metal particles saturated with molecular hydrogen exhibit an absorption band at 265 nm ( = 4.5 · 10³ L mol^–1 cm^–1). One-electron reduction of methylviologen by hydrogen is catalyzed by the colloidal palladium prepared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 313–316, February, 1996.     

Crystal Structures of Two New Holmium Polysulfides in the Series of Rare-Earth Polychalcogenides

The crystal structures of two polysulfide phases HoS_1.885(5) (I) and HoS_1.863(8) (II) were determined; the integer stoichiometric ratio was found to be Ho₈S₁₅. The data were collected on an Enraf-Nonius CAD-4 automatic diffractometer using the standard procedure (MoK, graphite monochromator, an absorption correction applied based on -scan data). Crystal I: space group P4/nmm, a = 3.820(1), c = 7.840(3) , V = 114.40(6) ³, Z = 2 for the composition HoS_1.885(5), d _calc = 6.542 g/cm³, R = 0.0520 for 184 unique reflections with I_hkl > 2 _I; crystal II: space group P2₁/m, a = 10.961(2), b = 11.465(2), c = 10.984(2) , = 91.27(3)°, V = 1380.0(4) ³, Z = 24 for the composition HoS_1.863(8), d _calc = 6.486 g/cm³, R = 0.0596 for 5354 unique reflections with I_hkl > 2 _I. In both compounds, the Ho atoms are surrounded by 9 (8+1 for three atoms in II) S atoms forming monocapped square antiprisms. The Ho–S distances vary from 2.717 to 3.067 irrespective of the type of ion [S^2– or (S₂)^2–]; the maximal distance to the atoms completing the coordination is 3.684 . The compounds have PbFCl type structures composed of ...(S₂)^2–...Ho³⁺...S^2–...S^2–...Ho³⁺...(S₂)^2–... layer packets differently oriented in space relative to the unit cell axes. The S^2–...S^2– and S^2–...(S₂)^2– interlayer distances are mostly shorter than the sum of the ionic radii and vary within the limits of 3.331-3.558 and 3.029-3.784 for the first and second types, respectively. For I, the calculated site occupancies and densities are given depending on the composition Ho-S_2-x (x = 0.25-0); for II, the most probable formulas of rational compositions in the same range of x are presented.     

Effect of acrylamide concentration on the kinetics of oxidation of tartaric acid by cerium(IV) in sulfuric-perchloric acid media

The kinetics of oxidation of tartaric acid by Ce(IV) in the absence and presence of acrylamide has been investigated spectrophotometrically in aqueous H₂SO₄–HClO₄ media at a constant ionic strength 2.0M and 25°C. Oxidation of tartaric acid in both cases was first order with respect to Ce(IV). Kinetic data showed that the reaction involves the formation of an unstable complex and an intermediate free radical. The activation parameters were calculated to be E _a =91.3±0.4 kJ-mol^–1, S=20.2±1.0 J-mol^–1-K^–1, H=88.8±0.4 kJ-mol^–1. A polymerization mechanism is discussed.     

Transformations of formaldehyde and glycolaldehyde during the hydroformylation of formaldehyde in the presence of rhodium catalysts

Hydroformylation of formaldehyde to give glycolaldehyde (GA) in the presence of RhCl(PPh₃)₃, RhCl(CO)(PPh₃)₂, or the RhCl₃ + PPh₃ system inN,N-dimethylacetamide was studied. The hydroformylation is accompanied by the Cannizzaro-Tishchenko reaction, condensation of CH₂O with GA to give C₃-C₁₆ polyoxyaldehydes (POA), and dimerization of GA. The formation of POA, which probably occurs through coordination of GA with a Rh atom, predominates among the side reactions. The optimum conditions for hydroformylation of CH₂O were found to be: RhCl₃ + PPh₃ as the catalyst,T 383 K, 12MPa, [H₂O] 1.8 mol L^–1, [Rh] 2.5 · 10^–3 g-at. L^–1, and [CH₂O] 0.03 g L^–1. At a substrate conversion of 62–67 %, the selectivity of GA formation reaches 96 %, and the yield is 60–65 %.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 75–78, January, 1995.     

Magnetische Untersuchungen an Komplexen von La(III), Pr(III) und Nd(III) mitSchiffschen Basen

Specific magnetic susceptibilities (_s) of several newly synthesized chelates of some of the lanthanons [La(III), Pr(III) and Nd(III)] are reported. These derivatives are of the general type,Ln(O-i-C₃H₇)_3–n (C₆H₅CHNRO) _n [where,Ln=La(III), Pr(III) or Nd(III);n=1 or 2 and R=CH₂CH₂, CH₂CHCH₃ or C₆H₄] and have been prepared by the reaction of the alkoxides of the lanthanons withSchiff bases such as benzylidene-2-hydroxyethylamine (C₆H₅CHNCH₂CH₂OH), benzylidene-2-hydroxy-n-propylamine (C₆H₅CHNCH₂CHOHCH₃) and benzylidene-o-aminophenol (C₆H₅CHNC₆H₄OH) in different molar relations in dry benzene.The resulting crystalline derivatives are non-volatile, light to deep yellow or blackish in colour. These tend to polymerize on keeping as shown by their insoluble nature and higher melting points, the polymerisation possibly occurring by the intermolecular coordination through oxygen atoms as reported earlier¹.UsingGouy method², the bis-isopropoxy mono-Schiff base and mono-isopropoxy bis-Schiff base complexes of La(III) have been shown to be diamagnetic, with _s values being in the range of –0.32 to –0.45×10^–6 and –0.39 to –0.55×10^–6 c.g.s. units at 305 K respectively.In the remaining derivatives, Pr(O-i-C₃H₇)_3–n (C₆H₅CH NRO) _n and Nd(O-i-C₃H₇)_3–n (C₆H₅CHNRO) _n (where,n=1 or 2 and R=CH₂CH₂, CH₂CHCH₃ or C₆H₄) the magnetic moment values range between 3.25 to 3.32 and 3.30 to 3.33 _B respectively indicating their paramagnetic nature.     

On the linear mixed valence compounds obtained by partial oxidation ofcis-diamminedichloroplatinum(II)

Summary The partial oxidation products ofcis-[Pt(NH₃)₂Cl₂] (Cisplatin) by (NH₄)₂S₂O₈ and by K₂PtCl₆, as well as the recrystallization of the former product in various solutions (HClO₄, NaClO₄, NaBF₄, NaHSO₄, H₂SO₄) have been re-examined. Contrary to the conclusions of previous works, the general formulation of these compounds iscis-[Pt²⁺(NH₃)₂Cl₂]X_x·yH₂O ( = 0.3–0.4, X = SO ₄ ^2– , PtCl ₄ ^2– , ClO ₄ ^2– , BF ₄ ^2– , HSO ₄ ^2– , ..., 0y 1). These materials are all linear chain Pt—Pt compounds belonging to the class III of Robin-Day compounds with Pt—Pt distances in the range 3.00–3.06 Å. The oxidation of Cisplatin by persulphate gives two sulphate compounds of the same formulation (x = 0.2), which differ in aspect, metallic character and spectral properties. Structural information was obtained from polarized micro-Raman spectra of a needle-like sample of the perchlorate and from X-ray powder diffraction spectra. The cell of the perchlorate was orthorhombic while the two sulphate forms had a monoclinic cell with slightly different parameters. Expansion of the Cisplatin interchain distance occurred only along one crystallographic direction. The two sulphate forms differed in the degree of order along this direction. An approximate structure is proposed and discussed in relation to the Cisplatin precursor.     

Study of the fluorite–pyrochlore–fluorite phase transitions in Ln<Subscript>2</Subscript>Ti<Subscript>2</Subscript>O<Subscript>7</Subscript> (Ln=Lu,Yb, Tm)

The ordering processes in Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) are studied by X-ray diffraction, thermal analysis, infrared absorption (IR) spectroscopy, and electrical conductivity measurements. The coprecipitation method followed by freeze-drying was used for Ln₂Ti₂O₇ synthesis. The region of low-temperature fluorite phase existence is 600 °C<T<740 °C. The low-temperature fluorite–pyrochlore phase transition in Ln₂Ti₂O₇ takes place at ~740–800 °C. Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) have the structure of disordered pyrochlore with antisite Ln–Ti defects at 800 °C<T<1,100 °C.The high-temperature pyrochlore–fluorite transformation takes place in Tm₂Ti₂O₇, Yb₂Ti₂O₇, and Lu₂Ti₂O₇ in air at T>1,600 °C. The conductivity values are 5·10^–3 S/cm for Tm₂Ti₂O₇, 6·10^–3 S/cm for Yb₂Ti₂O₇, and 10^–2 S/cm for Lu₂Ti₂O₇ at 740 °C. This order–disorder transition leads to a 2 orders of magnitude conductivity growth and a 10–30 times permittivity increase in Ln₂Ti₂O₇ samples obtained at 1,700 °C.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

Molecular structure of the cobalt(ii) chloride complex with triphenyl-N-(2-pyrimidyl)phosphineimine

An X-ray structural study of the cobalt(ii) chloride complex with triphenyl-N-(2-pyrimidyl)phosphineimine has been performed (automatic diffractometer, Mo-–K , 2916 observed reflections, the heavy-atom method, the least squares method in anisotropicisotropic approximation toR=0.043). The crystals are monoclinic,a=15.979(6) Å,b=17.391(6) Å,c=14.976(6) Å, =104.21(2)°,V=4034(5) ų,d _calc=1.384 g cm^–3,Z=4, space groupP2₁/c. The Co atom has a distorted tetrahedral coordination by two Cl atoms (2.268(2) Å and 2.278(3) Å) and two N atoms (2.030(4) Å and 2.025(5) Å) of the two pyrimidine heterocycles. The Cl-Co-Cl and N-Co-N bond angles are equal to 107.7(1)° and 123.4(2)°, respectively. Additional weak coordination of the Co atom by two N atoms of the imine groups [Co...N 2.982(4) Å and 3.045(4) Å] is also observed in the molecule of the complex, and this coordination changes the nearest environment of the Co atom to distorted octahedral coordination. The lengths of the phosphorus-imine P=N bonds are 1.596(6) Å and 1.585(6) Å. The results obtained are compared with previous structural investigations of similar complexes of transition metals with iminophosphoranes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1203–1206, July, 1993.     

Studies of artificial hydrolytic metalloenzymes: The catalyzed carboxyester hydrolysis by copper(II), zinc(II) and cobalt(II) complexes of the tripod ligand tris(2-benzimidazylmethyl)amine

The hydrolysis kinetics of p-nitrophenyl acetate (NA) catalyzed by Cu^II, Zn^II and Co^II complexes of tris(2-benzimidazylmethyl)amine (NBT) have been studied. The hydrolysis rate is first-order in both metal(II) complex and NA. The second-order rate constants, k_cat are 0.083, 0.241 and 0.285mol^–1Ls^–1 (298K, I = 0.10molL^–1 KNO₃, 0.02molL^–1 tris buffer, 40% MeCN aqueous solution) for Zn–NBT, Co–NBT and Cu–NBT complexes, respectively. The result indicates that the hydrolytic metalloenzyme activity of different metal complexes increases with the electrophilicity of the metal ions and that the complexes, in this paper, constitute that most efficient hydrolytic metalloenzyme models reported to date. An increase in MeCN content in the solution greatly reduces the hydrolytic activity of the nucleophiles.     

IR-Spectroscopic investigation of the hydration of tetrabutylammonium bromide in methylene chloride

The concentration dependence of the H₂O spectra in solutions of tetrabutylammonium bromide Bu₄NBr in methylene chloride was investigated by IR-spectroscopy. At low salt and H₂O concentrations the equilibrium: Br _f ^– +HOH_fBr^–HOH dominates where f indicates free or not hydrogen-bonded Br^– and H₂O. With increasing salt content, Br^–H–O–HBr^– complexes are present in addition. At high salt and H₂O content, including the saturated aqueous Bu₄NBr solution, H-bonded cyclic dimers seem to be important.Presented at the sixth Italian meeting on Calorimetry and Thermal Analysis (AICAT) held in Naples. December 4–7, 1984.     

Thermo-Gasanalysator zur Charakterisierung von Kohlenstoff- und Schwefelverbindungen in luftgetragenen St?uben

Zusammenfassung Die Charakterisierung von Kohlenstoff- und Schwefelverbindungen in korngrößenseparierend gesammelten Staubproben wird durch temperaturprogrammierte Zersetzung der Probe im Sauerstoffstrom und simultane Analyse von gebildetem CO₂ und SO₂ durchgeführt. Eine Unterscheidung von zwei organischen Kohlenstofffraktionen sowie von »Ruß-Kohlenstoff«, »Carbonatkohlenstoff«, »Konversionsschwefel«, »Ruß-Schwefel« und »Schwefel aus thermisch stabilen Sulfaten« in vier Korngrößenbereichen im Staubkollektiv 0,1–25 m AD ermöglicht die Zuordnung bestimmter Verbindungsgruppen zu verschiedenenen Bereichen des »Multimodalen Modells«. Zur Analyse werden 50–200 g Probe benötigt. Der Analysator besteht aus der Kombination eines temperaturprogrammierten Ofens mit gasanalytischen Monitoren für CO₂ und SO₂. Die Nachweisempfindlichkeit liegt bei 40 ng S s^–1 und 400 ng C s^–1 für vollen Schreiberausschlag (200 mm). In Anwendungsbeispielen wird der Einsatz der Methode zur Quellenanalyse von Aerosolen demonstriert.

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Thermo gas-analyzer for the characterization of carbonaceous and sulphurous compounds in atmospheric particles

Summary Characterization of carbonaceous and sulphurous compounds in size fractions of atmospheric particles is carried out by temperature programmed decomposition of the sample in oxygen atmosphere and simultaneous detection of evolved CO₂ and SO₂. The speciation of two organic carbon fractions, of soot carbon, carbonate carbon, converted sulphur, soot sulphur and sulphur from thermally stable sulphates in four size ranges of atmospheric particles (0.1–25 m AD) makes possible the classification into modes according to the multimodal model. For the analysis 50–200 g of sample is required. The analyzer, a combination of a temperature programmed furnace with instruments for monitoring of CO₂ and SO₂ is operated with a sensitivity of 40 ng S s^–1 and 400 ng Cs^–1 for recorder full-scale (200mm). Results of field tests demonstrate the application for aerosol source identification and conversion studies.

Der Autor möchte Herrn Prof. Dr. H. Malissa für die Anregungen und Diskussionen zur vorliegenden Arbeit vielmals danken. Mein Dank gilt auch Frl. Ing. Ch. Minich für die technische Assistenz bei der Durchführung der Analysen.Diese Arbeit wurde durch Mittel und Geräte des Bundesministeriums für Gesundheit und Umweltschutz unterstützt.     

Linear and Nonlinear Optical Properties of C60 Derivative Sol-Gels

Optical limiting properties of a sol-gel, functionalized with C₆₀ derivative molecule were studied by the nonlinear transmission technique in 480–650 nm wavelength range with nanosecond pulsed laser. The solid plates, with functionalized derivative C₆₀ concentration equal to 0.004 ML^–1, show interesting limiting behavior with threshold around 0.01 J/cm². The damage threshold ranges between 0.1 and 10 J/cm² depending upon the sample optical quality. The nonlinear optical properties of sol-gels were determined also by the optical third harmonic generation. At 1907 nm the cubic ⁽³⁾ (–3 ; , , ) susceptibility is of 1.3(± 0.1) × 10^–14 esu.     

Withasteroids ofPhysalis VI.1H and13C NMR spectra of withasteroids ixocarpalactone A and ixocarpanolide

The¹H and¹³C NMR spectra of two withasteroids isolated fromPhysalis ixocarpa Brot. have been studied in detail. Their spectral characteristics are discussed. A comparison of the results obtained has led to the identification of a withasteroid with the composition C₂₈H₄₀O₈, mp 291–292°C (from methanol) as ixocarpalactone A, in spite of some difference in its physical constants. The other compound, with mp 252–253°C (from methanol), had the composition C₂₈H₄₀O₆, [] _D ²⁰ +27±4°, is new and has been called ixocarpanolide. The structure of 5,20R-dihydroxy-1-oxo-6, 7-epoxy-22R-witha-2-enolide has been proposed for it.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 326–332, May–June, 1986.     

Dissociation quotients of malonic acid in aqueous sodium chloride media to 100°C

The first and second molal dissociation quotients of malonic acid were measured potentiometrically in a concentration cell fitted with hydrogen electrodes. The hydrogen ion molality of malonic acid/bimalonate solutions was measured relative to a standard aqueous HCl solution from 0 to 100°C over 25° intervals at five ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The molal dissociation quotients and available literature data were treated in the all anionic form by a seven-term equation. This treatment yielded the following thermodynamic quantities for the first acid dissociation equilibrium at 25°C: logK _1a =-2.852±0.003, H _1a ^/o =0.1±0.3 kJ-mol^–1, S _1a ^o =–54.4±1.0 J-mol^–1-K^–1, and C _p,1a ^o =–185±20 J-mol^–1-K^–1. Measurements of the bimalonate/malonate system were made over the same intervals of temperature and ionic strength. A similar regression of the present and previously published equilibrium quotients using a seven-term equation yielded the following values for the second acid dissociation equilibrium at 25°C: logK_2a=–5.697±0.001, H _2a ^o =–5.13±0.11 kJ-mol^–1, S _2a ^o =–126.3±0.4 J-mol^–1-K^–1, and C _p,2a ^o =–250+10 J-mol^–1-K^–1.Presented at the Second International Symposium on Chemistry in High Temperature Water, Provo, UT, August 1991.     

Complex formation between nickel(II) and 2-(2-aminoethyl) benzimidazole: A kinetic and equilibrium study

Summary The reversible complex formation between 2-(2-aminoethyl) benzimidazole (AEB) and nickel(II) was studied by stopped flow spectrophotometry at I = 0.30 mol dm^–3. Both the neutral and monoprotonated form of AEB reacted to give the NiAEB²⁺ chelate. At 25 °C, the rates and activation parameters for the reactions Ni_II + AEB NiAEB²⁺ and Ni^II + AEBH⁺ NiAEB²⁺ + H⁺ are k _f ^L(dm^–3 mol^–1 s^–1) = (2.17 ± 0.24) × 10³, H (kJ mol^–1) = 40.0 ± 0.8, S (JK^–1 mol^–1) = – 47 ± 3 and k _inff ^pHL (dm³ mol^–1 s^–1) = 33 ± 10, H (kJ mol^–1) = 42.0 ±2.7, S (JK^–1 mol^–1) = – 72 ± 9. The dissociation of NiAEB²⁺ was acid catalysed and k _obs for this process increased linearly with [H⁺] in the 0.01–0.15 mol dm^–3 (10–30 °C) range with k _H(dm³ mol^–1s^–1) (25 °C) = 329 ± 6, H (kJ mol^–1) = 40 ± 2 and S (JK^–1 mol^–1) = – 61 ± 8. The results also indicated that the formation of NiAEB²⁺ involves a chelation-controlled, rate-limiting process. Analysis of the S ° data for the acid ionisation of AEBH _inf2 ^p2+ and the formation of NiAEB²⁺ showed that the bulky AEBH⁺ ion has a solvent structure breaking effect as compared to AEB [s _aqS ° (AEBH⁺) – s _aq ° (AEB) = 69 JK^–1 mol^–1], while AEBH _inf2 ^p2+ is a solvent ordering ion relative to NiAEB²⁺ [s _aq° (NiAEB²⁺) – ovS _aq ° (AEBH _inf2 ^p2+ ) = 11 JK^–1 mol^–1].Author to whom all correspondence should be directed.     

Synthesis and crystal structure of an organic semiconductor (ET)4[Hg2I6]

A new cation-radical salt (ET)₄[Hg₂I₆] (1), where ET is bis(ethylenedithio)tetrathiafulvalene, has been synthesized in the system ET-HgI₃ ^–-PhCl. An X-ray study of 1 (a=41.02(5),b=23.01(1),c=8.233(2) Å,V=7772(3) ų, space groupPc2₁ b,Z=4,d _calc=2.308 g cm^–3) has established its composition, chemical formula, and the main structural features. The ET cation-radicals are packed in the conducting layer, the type of packing is ; the [Hg₂I₆]^2– anion has a dimeric structure. The temperature dependence of the conductivity of the (ET)₄[Hg₂I₆] crystals (₃₀₀=6 Ohm^–1 cm^–1) has a semiconducting character.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1240–1244, July, 1994.We thank M. G. Kaplunov for his participation in the discussion of the obtained results.This work was financially supported by the Scientific Council on the Problems of High-Temperature Superconductivity (Grant No. 90346 Metallorg) and the Russian Foundation for Basic Research (Project No. 93-02-2384).