Structure and vaporization of a gallium tribromide aminomethylpyridine complex

The structure of a gallium tribromide complex with 2-aminomethylpyridine (amPy) (1: 1) has been established by single-crystal X-ray diffraction for the first time. The complex has been shown to have the ionic structure [GaBr₂amPy₂]⁺[GaBr₄]^? in the condensed phase. The qualitative composition of the vapor over the complex has been determined by mass spectrometry within a temperature range of 80–250°C. The elimination of hydrogen bromide and 2-aminomethylpyridine proceed at 80–180°C to enrich the condensed phase with gallium tribromide. GaBr₂(amPy-H), GaBr₃amPy, GaBr(amPy-2H), and Ga₂Br₅(amPy-H) are the major gallium-containing vapor species at 250°C.     

Effect of cobalt(III) 1-nitroso-2-naphtholate on free-radical polymerization to vinyl monomers

It has been shown that, at 70°C, cobalt(III) 1-nitroso-2-naphtholate inhibits the free-radical polymerization of styrene, methyl methacrylate, butyl methacrylate, and butyl acrylate. The induction period linearly increases with complex concentration. The polymerization of styrene (120°C) carried out in the presence of cobalt(III) 1-nitroso-2-naphtholate shows typical features of pseudoliving polymerization, namely, linear ln[M]₀/[M]-time and molecular mass-conversion plots. When the monomers are allowed to stand with a complex (7 × 10^?3 mol/l) and an initiator (5 × 10^?3 mol/l) for 1 day at 20°C, the ESR signal corresponding to the nitroxide radical appears. In the course of polymerization, the signal disappears, indicating the consecutive transformation of the cobalt(III) 1-nitroso-2-naphtholate radical into the macronitroxide adduct. Polystyrene samples isolated at various conversions initiate the secondary polymerization of styrene and its block copolymerization with methyl methacrylate.     

Structure and magnetism of an exchange coupled system: An NMR approach

A binuclear copper(II) complex [Cu₂L(OH)](C1O₄)₂·2H₂O has been synthesized and characterized by X-ray crystallography and¹H-NMR studies. The crystal structure shows that the bridging angles between Cu(l)-O(l)-Cu(2) and Cu(l)-O(2)-Cu(2) are 98.9(2)° and 102.2(2)° respectively. The Cu(l)-Cu(2) distance is 3.0097(12)?. This indicates that the interaction between the two copper atoms is antiferromagnetic in nature. The geometry around Cu(l) is distorted square-pyramid with one water molecule occupying the axial fifth position, whereas, the geometry around Cu(2) is distorted square-planar with weak interactions of one of the perchlorate anion. There are eight molecules present in the unit cell. There is an interdimer interaction between the dimers. The temperature-dependent¹H-NMR chemical shift studies have been performed on six different protons of this complex which reveals that the exchange coupling constant (− 2J) is same for all protons (208 ± 1 cm⁻¹). However, the hyperfine coupling constant (A′) was found to be different in magnitude as well as in sign. We also report solvent dependent NMR properties.     

High temperature reactions of titanium(IV) oxide with some alkali persulfates and their decomposition products

The solid state reactions between TiO₂ and Na₂S₂O₈ or K₂S₂O₈ have been investigated using TG, DTG, DTA, IR, and X-ray diffraction studies in the range of 20 to 1000°C.It has been shown that TiO₂ reacts stoichiometrically (1 : 1) with Na₂S₂O₈ in the range of 160 and 220°C forming the complex sodium monoperoxodisulfato—titanium(IV) as characterized by IR and X-ray analysis. The new complex then decomposes into the reactants above 190°C.An exothermic reaction has been observed between TiO₂ and molten K₂S₂O₇ at mole ratio 1:2 respectively and higher, in the range of 280 and 350°C. The IR and X-ray analyses have shown the formation of a complex namely, potassium tetrasulfato titanium(IV) for which the formula and structure have been proposed. This complex decomposes at higher temperatures into K₂SO₄ and a mixed sulfate of potassium and titanium. The mixed sulfate melts at 620°C and decomposes into K₂SO₄, TiO₂, and the gaseous SO₃.On the other hand, Na₂S₂O₈ decomposes in a special mode producing a polymeric product of Na₁₀S₉O₃₂. Decomposition of this species occurs after melting at 560°C into Na₂SO₄ and sulfur oxides. The decomposition reaction has been proved to be catalysed by TiO₂ itself.     

Methylmercuric halide-halide complexation in ethanol solution

The formation constants for CH₃HgCl₂^? at 26°C (0.31 l/mole), and for CH₃HgBr₂^? at 26°C (0.94 l/mole) and at 60°C (0.70 l/mole) in ethanol solution have been determined from the variation of Hg NMR chemical shift (by INDOR) with composition of methylmercuric halide-lithium halide solutions. These data have been employed in a reexamination of the “one-anion” and “two-anion” catalysed reactions of mercuric bromide with alkylmercuric bromides.     

Synthesis and Crystal Structure of a New Sulfur-Palladium-Nitrogen Complex

The reaction of 4-amino-6-methyl-1,2,4-triazine-3(2H)-thione-5-one (AMTTO, 1 ) with palladium(II) chloride in acetonitrile/methanol leads to the N,S-coordinated complex [Pd(η²-AMTTO-N,S)Cl₂] · CH₃OH ( 2 ). 2 has been characterized by IR and MS techniques. The ligand 1 and the complex 2 were also investigated by X-ray structure determinations. 1 crystallizes in the space group P1¯ with the lattice dimensions at –70 °C: a = 419.6(1), b = 598.2(1), c = 1351.3(1) pm, α = 92.23(1), β = 91.20(1), γ = 100.51(1)°, Z = 2, R₁ = 0.0441. 2 crystallizes in the space group P2₁/c with the lattice dimensions at 20 °C: a = 683.3(1), b = 1323.0(1), c = 1254.2(1) pm, β = 92.61(1)°, Z = 4, R₁ = 0.0361. According to the structure analysis 1 consists of planar C,N-heterocycles connected by hydrogen bridges forming an infinite chain along [110]. The basic heterocyclic skeleton of 2 is essentially planar and linked three-dimensionally through hydrogen bridges.     

Ionic conductivity of Li7BiO6

The ionic conductivity of polycrystalline Li₇BiO₆ pellets has been measured by complex impedence method. The conductivity is 5.7 × 10^?3 (Ω cm)^?1 and 300°C and 3.8 × 10^?6 (Ω cm)^?1 at 100°C. Li₇BiO₆ is the best lithium conductor among the structurally related Li_nMO₆ compounds.     

2D hydrogen-bonded manganese–picolinate coordination network: ionic liquid-induced synthesis,crystal structure and thermogravimetric analysis

A new manganese coordination complex of formula [Mn(2-picolinate)₂·2H₂O]·H₂O based on 2-picolinic acid has been synthesized hydrothermally at 120 °C for 48 h in presence of ionic liquid tetraethylammonium hydroxide (25% methanolic solution). 1 crystallizes in monoclinic crystal system and is hydrogen-bonded metal-organic network in which aqua ligands are instrumental in deciding structural features. The reported complex 1 is insoluble in almost all organic solvents as well as in water and shows good thermal stability upto 450 °C.     

Vorstufen für polymere Silazane mit Fluoralkyl-Seitenketten und ihr Kondensationsverhalten

Preliminary Stages of Polymeric Silazanes with Fluoroalkyl Side Chains and their Condensation Behaviour Tetrakis(2,2,2-trifluoroethyl)aminosilane has been synthesized by aminolysis of silicon tetrachloride with 2,2,2-trifluorethylamine. The characterisation of the silane tetramine was carried out spectroscopically and by X-ray-methods. The thermal condensation has been investigated between 60°C and 300°C. At 300°C the formation of oligospirocycloorganoazanes was observed which have been identified spectroscopically. The new silane tetramine reacts with trimethylalumina in toluene. The product has been characterized by crystal structure analysis to be a dimeric (C₁₈H₂₆N₈F₂₄Si₂Al₂). (P1 ; a = 920.39(9), b = 943.32(2), c = 1235.4(1) pm, α = 68.8(7)°, β = 86.9(4)°, γ = 62.6(4)°, Z = 1, 3923 independent reflections; R = 0.059, Rw = 0.054)     

Complex Phosphates in the Li(Na)3]PO4-InPO4 Systems

Subsolidus sections in the systems Li₃PO₄-InPO₄ (950°C) and Na₃PO₄-InPO₄ (800, 900, and 1000°C) have been studied by X-ray powder diffraction. The compound Li₃In(PO₄)₂ has been synthesized, and the nasicon-type solid solution Li_{3(1 ? x)}In_{2 + x}(PO₄)₃ (0.67 ≤ x ≤ 0.80). has been found to exist. In the system Na₃PO₄-InPO₄, the solid solution Na_{3(1 ? x)}In_x/3PO₄ (0 ≤ x ≤ 0.2) and two complex phosphates exist: Na₃In(PO₄)₂ and Na₃In₂(PO₄)₃. These complex phosphates are dimorphic, with the irreversible-transition temperature equal to 675 and 820°C, respectively. Na₃In(PO₄)₂ degrades at 920°C. Ionic conductivity has been measured in some phases in the system.     

Characterization of Anilinepentacyanoferrate (II) and (III)

The anilinepentacyanoferrate (II) complex has been characterized in aqueous solution. The complex exhibits a predominant ligand field transition at λ_max = 415 nm with ?_max = 494 M^?1 cm^?1. The corresponding Fe(III) complex displays a strong absorption at λ_max = 700nm(?_max = 1.61×10⁴ M^?1 sec^?1) which can be assigned as a ligand to metal charge transfer transition. The rate constants of formation and dissociation for the Fc(II) complex are (3.14±0.18)×10² M^?1W^?1 and 0.985±0.005 sec^?1, respectively, at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C. The cyclic voltammetry of the complex shows that a reversible redox process is observed with E_1/2 value of 0.51±0.01 V vs. NHE at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C. The kinetic study of the oxidation of the Fe(II) complex by ferricyanide ion yielded the rate constant of the reaction k_et = (1.43±0.04)x10 M sec^?1 at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C.     

1:1 alternating copolymer of acrylonitrile and vinyl acetate

Copolymerization of the acrylonitrile-zinc chloride complex with excess vinyl acetate has been investigated. Alternating 1:1 copolymers of acrylonitrile and vinyl acetate of high molecular weights have been successfully prepared. The alternating structure has been ascertained by means of high-resolution nuclear magnetic resonance spectroscopy. The copolymer is amorphous (T_g = 85°C) and has shown thermal and oxidative stability better than those of polyacrylonitrile. The copolymer is soluble in acetone as well as in more powerful solvents such as dimethylformamide, dimethyl sulfoxide, nitromethane, and N-methylpyrrolidone. The copolymer has been processed into films and fibers from its acetone solutions. Films show tensile properties similar to those of cellulose acetate under ambient conditions; they suffer drastic loss in tensile properties at above 50°C and retain their good tensile properties at subzero temperatures (determined as low as ?40°C). Fibers show tensile properties comparable to those of modacrylic fibers under ambient conditions but suffer marked loss in stiffness at 40°C in water and 60°C in air. The fibers also retain their good properties at subzero temperatures (measured down to ?60°C).     

Synthesis and crystal structure of [Co(mpt)_2{P(OCH_3)_3}_2]BF_4 (Hmpt = 2-mercaptothiazoline)

The monomeric cobalt-phosphite-thiolato complex [ Co (mpt)2 {P (OCH3 )3 }2 ] BF4 (Hmpt = 2-mercaptothiazoline) has been prepared and characterized by X-ray crystallography. The complex crystallizes in the monoclinic space group C2/c with a= 0.8078(5), b=2.6020(18), c=1.2191(7) nm, β= 99.38 (1)°, V= 2.528(3) nm3, and Z = 4. The structure comprises discrete cations [Co(mpt)2{P(OCH3)3}2.] and anions BF4- , in which the cobalt (Ⅲ) atom is coordinated to two chelate mpt- and two as-oriented monodentate P(OCH3)3 ligands in a highly distorted octahedral geometry. The most distorted angles are S(2)-Co(1)-S(2a) of 162.23(10)° and N(1)-Co(1)-S(2) of 71. 47 (13)°, the latter is caused by the geometric constraint of the bidentate ligand mpt- . Cyclic voltammetry has been used to study the electrochemical behavior of the title complex on the R electrode in MeCN solution with 0.1 mol·L-1 of Bun4NBF4 as electrolyte. The results indicate that the title complex is unstable in MeCN.     

Calcichrome: a re-examination of its structure and chemical properties by solid- and liquid-state NMR,infrared spectroscopy,and selective chemical degradation

Nuclear magnetic resonance and infrared spectroscopies were used to unravel the controversies regarding the structures of calcichrome and calcion. Together with the identification of the products from selective chemical cleavage reactions, these data indicate that structures of both compounds are equivalent with a molecular formula of C₂₀H₁₄N₂O₁₅S₄·3H₂O (2,8,8′-trihydroxy-1,1′-azonaphthelene-3,6,3′,6′-tetrasulfonic acid). The compound has two titratable phenolic protons in aqueous solution with pK_a values of 7.19 ± 0.05 and 11.63 ± 0.05 at 25 ° C. As a ligand, the compound forms a colored complex with calcium(II) at a 1:1 stoichiometric ratio (pH 12.3) with a formation constant of 8.0 × 10³ at 25 ° C. The free form of the ligand at pH 12.3 has a molar maximum molar absorptivity of 1.44 × 10⁴ l mol^?1 cm^?1 at 599 nm, whereas the complexed form has a maximum molar absorptivity of 1.37 × 10⁴ l mol^? cm^?1 at 522 nm.     

Kinetics of α-olefin metathesis over the heterogeneous catalytic system (MoOCl<Subscript>4</Subscript>/SiO<Subscript>2</Subscript>)-SnMe<Subscript>4</Subscript>

The kinetics of 1-hexene and 1-octene metathesis over the (MoOC_l4/SiO₂)-SnMe₄ catalytic system at 27 and 50°C has been investigated. The rate constants of the forward and reverse reactions and the catalyst deactivation constants have been measured. The number of active sites has been determined to be 10–13 mol % of the total number of molybdenum atoms.     

Zum Aufbau Schlecht geordneter Calciumhydrogensilicate. II. Über eine aus Poly- und Disilicat bestehende Phase

On the Structure of Ill-crystallized Calcium Hydrogen Silicates. II. A Phase Consisting of Poly and Disilicate Both by condensation reactions of a calcium hydrogen disilicate phase [1] under the mother liquid at 80°C and by hydrothermal reactions of lime and silica at 150°C an ill-crystallized calcium hydrogen silicate phase is formed, being built up by nearly equal parts (referred to Si) of poly-and disilicate anions. The CaO content of the phase synthesized at 80°C varies between 1.1 and 2CaO/SiO₂, depending on the Ca(OH)₂ concentration in the mother liquid. In the phase formed at 150°C is CaO/SiO₂ = l.l–l.5. A proposal for the constitution of this phase is given.     

Kinetik und mechanismus der epoxidierung von allylalkohol mit peroxykomplexen des molybdäns (VI)

The kinetics of the allylalcohol epoxidation by peroxycomplexes MoO(O₂₂L₁L₂ (1) and MoO(O₂)₂L₁ (2), where L₁=hexamethylphosphotriamide, L₂ = H₂O, has been studied in 1,2- dichlorethane within the 30–60°C temperature range. The reaction-rate observed by the oxygen content decreased is directly proportional to the concentration of both complexes. The reaction rate dependence on the allylalcohol concentration is described by the Michaelis-Menten equation. The parameters of this equation were determined at 50°C. K_m is equal to 0·78 and 0·81 Mol/l for 1 and 2 respectively. The activation energy values are 16·1 ± 0·5 and 18·3 ± 1·0 Kcal/Mol for 1 and 2, respectively. The glicidol yield at 50°C is varying from 70 to 100% for 2 and from 65 to 75% for 1 depending on the convertion level of the reaction. The epoxidation mechanism of allylalcohol by covalent molybdenum (VI) peroxy-complexes is discussed.     

Studies of the kinetics of the interaction between N-trifluoroacetlyl-D-tryptophan and α-chymotrypsin by pulsed nuclear magnetic resonance

The Carr-Purcell experiment first used by Allerhand and Gutowsky for the determination of chemical exchange rates has been applied to the study of an enzyme inhibitor complex. Chemical shift and relaxation time data obtained by analysis of pulsed fluorine NMR data collected at 51 MHz are shown to be consistent with high resolution results assembled at 94° 1 MHz. The rate constants for dissociation of the N-trifluoroacetyl-D -tryptophan-α-chymotrypsin complex were determined to be 1 × 10⁴ s^?1 at 26°C and 2 × 10³ s^?1 at 6·5°C. The resonance position of the fluorine nuclei of the inhibitor is shifted downfield ～1 ppm upon complexation to the enzyme, and the trifluoromethyl group suffers some restriction of molecular motion in the bound state as indicated by T₁ and T₂ data.     

Über Chalkogenolate. 89. Untersuchungen über N-Dicyandithiocarbamidsäure Darstellung und Eigenschaften der freien Säure

On Chalcogenolates. 89. Studies on N-Dicyandithiocarbamic Acid. Preparation and Properties of the Free Acid Colorless N-dicyandithiocarbamic acid (melting point: 112°C) has been prepared by reaction between a suspension of K[S₂C? N(CN)₂] in diethyl ether and a solution of HCl in (C₂H₅)₂O at 0°C; the ether was distilled off at 0°C in vacuo. The compound has been characterized by means of infared spectra, electron absorption spectra, ¹H-NMR spectra, and mass spectra. The dissociation constant of N-dicyandithiocarbamic acid in water is K_a = (1.69 ± 0.1) X 10^?1 20°C. The thermodynamic data of the dissociation were calculated.     

Donnan Exclusion Chromatography Application to Complex Formation Studies

Abstract

A new method for the evaluation of stability constants of complex species has been proposed, based on the principle of Donnan exclusion chromatography. The stability constants for trimetaphosphate complexes of magnesium and calcium ions have been evaluated to be log β₁ = 1.50 and 1.64 (I=1.00, 25° ± 2°C), respectively.