Interaction of poly(vinyl acetate) radical with iron (III) complexes

The polymerization of vinyl acetate in N,N-dimethylformamide (DMF) at 60°C initiated by AIBN in the presence of [Fe(DMF)₆](ClO₄)₃ and Fe(N₃)₃ had been studied. Fe(N₃)₃ was produced in situ by mixing solid sodium azide (NaN₃) and hexakis(N,N-dimethylformamide) iron (III) perchlorate, [Fe(DMF)₆](ClO₄)₃, in the ratio of 3:1. The velocity constant k_x for the interaction of poly(vinyl acetate) radical with [Fe(DMF)₆]³⁺ was found to be 1.44 × 10³L mol^?1 s^?1 and that for the interaction of poly(vinyl acetate) radical with Fe(N₃)₃ to be 3.44 × 10⁵ L mol^?1 s^?1 at 60°C.     

Effects of iron(III) chloro complexes on the polymerization of styrene

The polymerization of styrene initiated by 2,2′-azobisisobutyronitrile has been studied in N,N-dimethylformamide solution at 60°C in the presence of hexakis(N,N-dimethylformamide) iron(III) tetrafluoroborate alone, and also in the presence of added lithium chloride. The presence of Fe(DMF)₆³⁺ ions in the polymerizing systems caused retardation, but iron(III) chloro complexes produced well defined inhibition periods. Velocity constants at 60°C for polystyryl radicals towards Fe(DMF)₆³⁺, Fe(DMF)₅Cl²⁺, Fe(DMF)₄Cl₂⁺, and FeCl₄^? ions were calculated to be 847, 4.15 × 10⁴, 6.55 × 10⁴, and 3.14 × 10⁴ l./mole-sec, respectively. Values of the initiator efficiency f for most systems investigated ranged from 0.59 to 0.62.     

The interaction of polystyryl radical with Cu(DMF)2Cl2

Kinetics of 2,2′-azobisisobutyronitrile initiated polymerization of styrene in N,N-dimethylformamide (DMF) were investigated in the presence of dichloro bis(N,N-dimethylformamide)copper(II) complex. The complex was prepared in situ by mixing tetrakis(N,N-dimethylformamide)copper(II) perchlorate with LiCl in the molar ratio of 1:2. The equilibrium constant for

was calculated by the limiting logarithmic method as 1.07 × 10¹⁰ l² mol^?2. The velocity constant at 60 for the interaction of polystyryl radical with Cu(DMF)₂Cl₂ is 2.16 × 10⁴ l. mol^?1 sec^?1.     

Studies on the reaction N + N3 → N2(B 3Πg) + N2(X 1Σ+g)

Strongly enhanced N₂ first positive emission N₂(B ³Π_g → A ³Σ⁺_u) has been observed on addition of N atoms into a flowing mixture of Cl and HN₃. The dependence of the emission intensity on N atom concentration gave a rate constant for the reaction N + N₃ → N₂(B ³Π_g) + N₂(X ¹Σ⁺_g) of _i(1.6 ± 1.1) × 10^?11 cm³ molecule^?1 s^?1. That for the reaction Cl + HN₃ → HCl + N₃ is (8.9 ± 1.0) × 10^?13 cm³ molecule^?1 s^?1 from the decay of the emission. Comparison of the emission intensity in ClHN₃ with that in ClHN₃N gave the rate constant of the reaction N₃ + N₃ → N₂(B ³Π_g) + 2N₂(X ¹Σ⁺_g) as 1.4 × 10^?12 cm³ molecule^?1 s^?1 on the assumption that N + N₃ yields only N₂(B ³Π_g) + N₂(X ¹Σ⁺_g).     

Cyanogen pyrolysis and the CN + NO reaction behind incident shock waves

The reaction chemistry of C₂N₂? Ar and C₂N₂? NO? Ar mixtures has been investigated behind incident shock waves. Progress of the reaction was monitored by observing the cyano radical (CN) in absorption at 388.3 nm. A quantitative spectroscopic model was used to determine concentration histories of CN. From initial slopes of CN concentration during cyanogen pyrolysis, the rate constant for C₂N₂ + M → 2CN + M (1) was determined to be k₁ = (4.11 ± 1.8) × 10¹⁶ exp(?47,070 ± 1400/T) cm³/mol · s. A reaction sequence for the C₂N₂? NO system was developed, and CN profiles were computed. By comparison with experimental CN profiles the rate constant for the reaction CN + NO → NCO + N (3) was determined to be k₃ = 10^{(14.0 ± 0.3)} exp(?21,190 ± 1500/T) cm³/mol · s. In addition, the rate of the four-centered reaction CN + NO → N₂ + CO (2) was estimated to be approximately three orders of magnitude below collision frequency.     

Beiträge zur Chemie der Halogensilan-Addukte. XVI. Darstellung,Eigenschaften, Kristall- und Molekülstruktur von Hexa(N,N-dimethylformamid)silicium(IV)-tetraiodid, [Si(OCHN(CH3)2)6]I4

Contributions to the Chemistry of Halosilane Adducts. XVI. Synthesis, Properties, Crystal and Molecular Structure of Hexa(N,N-dimethylformamide)silicon(IV)-tetraiodide When SiI₄ is reacted with DMF ionization of all SiI bonds occurs to give ( 2 ) (reaction of pure components) or ( 1 ) (CHCl₃ solution). IR and ¹H-NMR spectra are in accordance with the formation of the octahedral cation [Si · 6 DMF]⁴⁺, DMF being coordinated through the CO group. 1 is only slowly attacted by methanol or water DMF being liberated. 1 crystallizes in the monoclinic space group C2/c with 4 formula units per unit cell. The cation [Si · 6 DMF]⁴⁺ has 1 symmetry. DMF is coordinated to Si in trans-configuration with respect to NMe₂ with donation by oxygen. SiO bond distances (175.4–177.2 pm) correspond to those of [Si(O₂C₆H₄)₃]^2? and [Si(acac)₃]⁺; an increase of the CO distances (126.1–128.9 pm) and decrease of the CN distances (126.4–129.1 pm) as compared to free DMF is observed. These changes and structural data are discussed.     

Rate constant of the gas-phase reaction between Fe atoms and CO2

The rate constant of the gas-phase reaction Fe(a ⁵ D ₄) + CO₂ at 1180–2380 K and a total gas density of (7.0–10.0) × 10^?6 mol/cm³ behind incident shock waves is k(Fe + CO₂) = 1.4 × 10^{14.0 ± 0.3}exp[?(14590 ± 1100)/T] cm³ mol^?1 s^?1, as determined by resonance atomic absorption photometry. Using thermochemical data available from the literature, the rate constant of the reverse reaction was calculated to be k(Fe + CO) = 9.2 × 10^{11.0 ± 0.3} (T/1000)^0.57exp[?(490 ± 1100)/T] cm³ mol^?1 s^?1. The results are compared with data reported earlier.     

Solvation effect in thermal decomposition of 2,2′-azoisobutyronitrile on the N,N-dimethylformamide/acrylonitrile system

The thermal decomposition rate constant of AIBN (k_d) in N, N-dimethylformamide (DMF)/acrylonitrile (AN) mixtures of various compositions at 60°C is studied. The k_d value is (6.45 ± 0.3) × 10⁻⁴ min⁻¹ for pure DMF and (7.20 ± 0.3) × 10⁻⁴ min⁻¹ for pure acrylonitrile. The k_d values of DMF/AN mixtures were found to be dependent on the mixture composition. This dependence is not a linear function of the monomer mole fraction (x_M), but has a minimum at ca. 70 mol % of AN. The relationship k_d = f(x_M) has been interpreted on the basis of the hypothesis of initiator solvation by monomer AN and solvent DMF. © 1996 John Wiley & Sons, Inc.     

Volumes of Activation for Dimethylsulfoxide and N,N-Dimethylformamide Exchange with Hexasolvates of Aluminium (III) and Gallium (III) Ions in Deuterionitromethane Solution

High-pressure ¹H-NMR. has been used to determine volumes of activation (ΔV#) for solvent exchange with [M(S)₆]³⁺ ion (M = Al(III), Ga(III); S = dimethylsulfoxide (DMSO) and N,N-dimethylformamide (DMF)) in [²H]₃-nitromethane solution. For Al(III),Δ V# = + 15.6 ± 1.4 (S = DMSO, 358.5 K) and ΔV# = + 13.7 ± 1.2 cm³mol^?1 (S = DMF, 354.5 K), whilst for Ga(III), ΔV# = + 13.1 ± 1.0 (S = DMSO, 334.6 K) and ΔV# = +7.9 ± 1.6 cm³mol^?1 (S= DMF, 313.8 K). Variable temperature studies over a temperature range of 107.2 K (Al(III)) and 101.1 K (Ga(III)) were carried out for solvent exchange with [M(DMF)₆]³⁺ ions in [²H]₃-nitromethane solution, using stopped-flow NMR, and conventional linebroadening, and gave ΔH# = 88.3 ± 0.9 and 85.1 ± 0.6 kJ+ mol^?1, and ΔS# = 28.4 ± 2.7 and 45.1 ± 1.9 JK^?1 mol^?1 for Al(III) and Ga(III) ions respectively. All of these results are consistent with dissociative modes of activation.     

Potassium bis(ethylenediamine)­copper(II) ferricyanide

The title compound, potassium bis(ethylenediamine‐N,N′)copper(II) hexacyanoferrate(III), K[Cu(C₂H₈N₂)₂]‐[Fe(CN)₆], contains [Cu(en)₂]²⁺ and [Fe(CN)₆]^3? complex ions, where en is ethylenediamine. The Fe^III and K⁺ ions lie on twofold axes and the Cu^II atom lies on an inversion center. The [Cu(en)₂]²⁺ ion has square‐planar coordination with a mean Cu—N distance of 1.992 (2) Å and the [Fe(CN)₆]^3? ion has distorted octahedral coordination with a mean Fe—C distance of 1.947 (2) Å.     

Synthesis, crystal structure and thermal decomposition of a novel praseodymium supermolecular complex

A novel complex, [Pr(5-nip)(phen)(NO3)(DMF)] (5-nip: 5-nitroisophthalic acid; phen: 1,10-phenanthroline, DMF: N,N-dimethylformamide), was prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectrum and DTG-DSC techniques. The results show that the crystal is monoclinic, space group P2(1)/n with a=11.0876(6) Å, b=12.8739(7) Å, c=16.9994(8) Å; β=91.193(4)°, Z=4, D _c=1.822 Mg m^–3, F(000)=1320. Each Pr(III) ion is nine-coordinated by one chelating bidentate and two monodentate bridging carboxylate groups, one chelating bidentate nitryl group, one DMF molecule and one 1,10-phenanthroline molecule. The complex is constructed with one-dimensional ribbons featuring dinuclear units and the one-dimensional ribbons are further assembled into two-dimensional networks by strong π–π stacking interactions. The complex has high stability up to 500°C. The enthalpy change of formation of the compound in DMF was measured using an RD496-III type microcalorimeter with the value of –9.214±0.173 kJ mol^–1.     

Effect of solvent on the stability constant of complex formation and the thermodynamic parameters between dicyclohexyl-18-crown-6 with Eu3+, La3+, Er3+ and Y3+ cations

The complexation reaction between Eu³⁺, La³⁺, Er³⁺ and Y³⁺ cations with the dicyclohexyl-18-crown-6 (DCH18C6) in acetonitrile (AN)–dimethylformamide (DMF) and AN–methanol (MeOH) binary systems have been studied at different temperatures using conductometric method. The conductometric data show that the stoichiometry of the complexes is 1:1 [ML]. The results show that the stability constant of complexes in various solvents is: AN > MeOH > DMF. In the some cases, the minimum of logK_f for (DCH18C6–Eu³⁺), (DCH18C6–La³⁺), (DCH18C6–Er³⁺) and (DCH18C6–Y³⁺) complexes in AN–MeOH binary systems obtain at χ_MeOH ~ 0.75, and also, the logK_f of (DCH18C6–Er³⁺) complex in AN–DMF binary systems show a minimum at χ_AN ~ 0.75. Non-linear behavior was observed for the stability constant of complexes versus the composition of the solvent systems. The experimental data show that the selectivity order of DCH18C6 for these cations in AN–MeOH binary systems (mol% AN = 50, 75) at 25 °C is: Y³⁺ > Er³⁺ > Eu³⁺ > La³⁺. The values of thermodynamic parameters (?H?_C) for formation of complexes were obtained from temperature dependence of stability constants of complexes using the van′t Hoff plots and the standard entropy (?S?_C) were calculated from the relationship: ?G?_C, 298.15 = ?H?_C ?298.15?S?_C. The results show that the values of these thermodynamic parameters are influenced by the nature and the composition of the binary systems.     

Polymerization of methyl methacrylate by charge transfer mechanism by melamine and iron(III) complex

Methyl methacrylate (MMA) can be polymerized by the charge-transfer complex formed by the interaction of melamine (MM), MMA and carbon tetrachloride in a non-aqueous solvent like dimethyl sulphoxide (DMSO) or N-N-dimethylformamide. The polymerization can be accelerated by Lewis acids like Fe^3?. This paper reports the polymerization of MMA initiated by MM and CCl₄ and accelerated with hexakis dimethylsulphoxide iron(III) perchlorate [Fe(DMSO)₆] (ClO₄)₃. A, at 60°. Induction periods were observed for the polymerization initiated by MM and CCl₄ alone, but not when the molar ratio of MM to A became 3:1. The molecular weights of the polymers with 3:1 molar ratio of MM to A were higher than with MM alone. The rate constant for the polymerization of MMA in presence of [Fe(MM)₃]³⁺ was 1.4181 × 10^?5 1 mol^?1 sec^?1 at 60°. The transfer constant for CCl₄, in the absence of A, is 4.66 × 10^?3.     

The formation of an antitubercular complex [Fe(CN)5(INH)]3− through mercury(II)‐catalyzed ligand substitution reaction: A kinetic and mechanistic study

The kinetics and mechanism of the formation of an antitubercular complex [Fe(CN)₅(INH)]^3? based on the substitution reaction between K₄[Fe(CN)₆] and isoniazid (INH), i.e., isonicotinohydrazide, catalyzed by Hg²⁺ in aqueous medium was studied spectrophotometrically at 435 nm (the λ_max of the golden‐yellow‐colored complex [Fe(CN)₅(INH)]^3?) as a function of pH, ionic strength, temperature, and the concentration of the reactants and the catalyst. The replacement of coordinated CN^? in [Fe(CN)₆]^4? was facilitated by incoming ligand INH under the optimized reaction conditions: pH 3.5 ± 0.02, temperature = 30.0 ± 0.1°C, and ionic strength I = 0.05 M (KNO₃). The stoichiometry of the reaction and the stability constant of the complex ([Fe(CN)₅(INH)]^3?) have been established as 1:1 and 2.10 × 10³ M, respectively. The rate of catalyzed reaction was found to be slow at low pH values, to increase with increasing pH, to attain a maximum value at 3.50 ± 0.02, and finally to decrease after pH > 3.5 due to less availability of H⁺ ions needed to regenerate the catalytic species. The initial rates were evaluated for each variation from the absorbance versus time curves. The reaction was found to be pseudo‐first order with respect to [INH] and first order with respect to [Fe(CN)₆^4?] at lower concentration, whereas it was found to be fractional order at higher [INH] and [Fe(CN)₆^4?]. The ionic strength dependence study showed a negative salt effect on the rate of the reaction. Based on experimental results, a mechanism for the studied reaction is proposed. The rate equation derived from this mechanism explains all the experimental observations. The evaluated values of activation parameters for the catalyzed reaction suggest an interchange dissociative (I_d) mechanism. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 398–406, 2012     

Study on kinetics and mechanism of copper-catalyzed oxidation of hydrazine by iron (III) in acid solution

The copper-catalyzed oxidation of hydrazine by iron(III) in acid solution follows the rate law -d[Fe(III)]/dt = kK_h[Cu(II)]²/(K_h + [H⁺]), where K_h is the hydrolysis constant of Cu²⁺, k was found to be 8.8±0.8, 13.2±1.4 and 17.5±1.3 min^?1 at 35, 40, and 45°C respectively and μ= 0.2 mol/L. The composition of the activated complex is Cu²⁺, CuOH⁺, N₂H₄, H⁺ or others. Perhaps several hydrazine complexes of Cu(II) participate in the reaction and one of them isolated was Cu(N₂H₄)₂(HSO₄)₂. Study on the oxidation of this complex is also in conformity with the above rate law.     

Electrolytically generated sulfur dioxide anion radical S2O·−4, its absorption coefficient and some of its decay reactions

The electrochemical reduction of SO₂ in dimethylformamide at Pt electrodes finally leads to the red species S₃O^2?₆ via the blue complex S₂O^·?₄. The UV-VIS absorption coefficients are determined: ?(S₂O^·?₄) = (224 ± 25) × 10⁵ cm² mol^?1; ?(S₃O^2?₆) = (0.64 + 0.07) × 10⁵ cm² mol^?1. A calculation of the complexing constant of SO₂ with free SO^·?₂ radical based on potential shifts confirms this constant to be in the range of 200–700 1 mol^?1.Two potentiometric titration methods (viz: with allylbromide and tetraethylammoniumtribromide) for analysis of electrolytically generated S^III-oxo-anions in DMF are presented. Reactions of those anions with aromatic aldehydes and trials for trapping of possibly formed SO are described.     

A mixed‐valence iron complex of the antitumour drug 6‐mercaptopurine: tris(6‐mercaptopurine)iron(II) tetrachloroferrate(III) chloride

Single crystals of the title complex, tris(1,6‐di­hydro‐9H‐purine‐6‐thione‐N⁷,S)­iron(II) tetra­chloro­ferrate(III) chloride, [Fe(C₅H₄N₄S)₃][FeCl₄]Cl, were grown on the surface of solid 6‐mercaptopurine monohydrate pellets in a solution of iron(III) chloride. The solution of the hexagonal structure required the application of twin refinement techniques. All the component ions lie on threefold rotation axes. The complex contains distorted octahedral [Fe(C₅H₄N₄S)₃]²⁺ cations with three N7/S6‐chelating neutral 6‐mercaptopurine ligands, tetrahedral [FeCl₄]^? anions with a mean Fe—Cl distance of 2.189 (1) Å, and free chloride ions.     

Synthese und Kristallstrukturen von heteronuklearen AgI/FeII‐Koordinationspolymeren: (Me3PhN)2[Ag2Fe(SCN)6], (Me3PhN)6[Ag6Fe3(ECN)18] (E = S,Se) und (Me3PhN)4[Ag2Fe(SCN)8]

The reaction of AgSCN with (Me₃PhN)₃[Fe(NCS)₆] in DMF yields two‐dimensional polymeric, heteronuclear complexes (Me₃PhN)₂[Ag₂Fe(SCN)₆] ( 1 ) and (Me₃PhN)₆[Ag₆Fe₃(SCN)₁₈] · CH₂Cl₂·DMF ( 2a ) with bridging SCN^? ligands, whereas additional (Me₃PhN)(SCN) leads to (Me₃PhN)₄[Ag₂Fe(SCN)₈] ( 3 ) with a one‐dimensional structure. The selenocyanato complex 2b , homologous to 2a , could also be prepared. Single crystal X‐ray structure determinations show, that the Ag⁺ ions in 1 and 2a are coordinated tetrahedrally by four S atoms, in 3 by one N and three S atoms of the bridging SCN^? ligands; six N atoms of the SCN^? or SeCN^? ligands bind to Fe²⁺ in an octahedral arrangement.     

Cavity ring‐down study of BrO radicals: Kinetics of the Br + O3 reaction and rate of relaxation of vibrationally excited BrO by collisions with N2 and O2

Cavity ring‐down (CRD) techniques were used to study the kinetics of the reaction of Br atoms with ozone in 1–205 Torr of either N₂ or O₂, diluent at 298 K. By monitoring the rate of formation of BrO radicals, a value of k(Br + O₃) = (1.2 ± 0.1) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ was established that was independent of the nature and pressure of diluent gas. The rate of relaxation of vibrationally excited BrO radicals by collisions with N₂ and O₂ was measured; k(BrO(v) + O₂ → BrO(v − 1) + O₂) = (5.7 ± 0.3) × 10⁻¹³ and k(BrO(v) + N₂ → BrO(v − 1) + N₂) = (1.5 ± 0.2) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹. The increased efficiency of O₂ compared with N₂ as a relaxing agent for vibrationally excited BrO radicals is ascribed to the formation of a transient BrO–O₂ complex. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 125–130, 2000     

Synthesis,structure, and magnetic properties of heterotrimetallic tetranuclear complexes

Two novel heterotrimetallic tetranuclear complexes [Cu(H₂L)(CH₃OH)]₂Gd(DMF)Fe(CN)₆·2H₂O·DMF (1) and [Cu(H₂L)(CH₃OH)]₂Tb(H₂O)_0.57(DMF)_0.43Fe(CN)₆·5.5H₂O (2) are reported (H₄L = N,N′-ethylenebis(3-hydroxysalicylidene)). The central Ln(III) ion is surrounded by two neutral [Cu(H₂L)(CH₃OH)] moieties, forming a Cu₂Ln trinuclear unit. The [Fe(CN)₆]^3? anion is weakly coordinated to one Cu(II) ion of [Cu(H₂L)(CH₃OH)] through a cyanide nitrogen atom with the N–Cu distance of ca. 3.2 Å. Magnetic susceptibility measurements indicate the presence of overall ferromagnetic interactions in complexes 1 and 2. The magnetic coupling constant in complex 1 is J _Cu1Gd1 = 4.54 cm^?1 and J _Cu2Gd1 = 7.97 cm^?1 based on \( \hat{H} = - 2J_{\text{Cu1Gd1}} \hat{S}_{\text{Cu1Gd1}} - 2J_{\text{Cu2Gd1}} \hat{S}_{\text{Cu2Gd1}} \) . Dynamic AC magnetic susceptibility studies reveal that complex 2 shows frequency-dependent out-of-phase signals, typical of single molecule magnet behavior. The energy barrier for complex 2 under a 2 kOe applied DC magnetic field is 13 K.