Thermal decomposition of hydrotalcite with hexacyanoferrate(II) and hexacyanoferrate(III) anions in the interlayer

The mechanism for the decomposition of hydrotalcite remains unsolved. Controlled rate thermal analysis enables this decomposition pathway to be explored. The thermal decomposition of hydrotalcites with hexacyanoferrate(II) and hexacyanoferrate(III) in the interlayer has been studied using controlled rate thermal analysis technology. X-ray diffraction shows the hydrotalcites have a d(003) spacing of 10.9 and 11.1 Å which compares with a d-spacing of 7.9 and 7.98 Å for the hydrotalcite with carbonate or sulphate in the interlayer. Calculations show dehydration with a total loss of 7 moles of water proving the formula of hexacyanoferrate(II) intercalated hydrotalcite is Mg₆Al₂(OH)₁₆[Fe(CN)₆]_0.5·7H₂O and 9.0 moles for the hexacyanoferrate(III) intercalated hydrotalcite with the formula of Mg₆Al₂(OH)₁₆[Fe(CN)₆]_0.66·9H₂O. CRTA technology indicates the partial collapse of the dehydrated mineral. Dehydroxylation combined with CN unit loss occurs in two isothermal stages at 377 and 390°C for the hexacyanoferrate(III) and in a single isothermal process at 374°C for the hexacyanoferrate(III) hydrotalcite.     

Mild template synthesis in the iron(III)-ethanedithioamide-1,2-formaldehyde triple system on a K[Fe2(CN)6] gelatin-immobilized matrix

Complexation of Fe^III, in the form of K[Fe₂(CN)₆] gelatin-immobilized matrix, in contact with aqueous-alkaline solutions (pH ～ 12) containing ethanedithioamide-1,2 and formaldehyde, has been studied. Template synthesis leading to a chelate Fe^III coordination compound with a tetradentate N,N,S,S-donor ligand identified as 4,4,6-trimethyl-1,9-diamino-1,9-dimercapto-3,7-diazanon-3-en-2,8-dithione and hydroxy co-ligand occurs under these specific conditions. Ethanedithioamide-1,2 and formaldehyde are the ligand synthons in the process studied.     

Ruthenium(III) catalyzed oxidation of hexacyanoferrate(II) by periodate in aqueous alkaline medium

Ruthenium(III) catalyzed oxidation of hexacyanoferrate(II) by periodate in alkaline medium is assumed to occurvia substrate-catalyst complex formation followed by the interaction of oxidant and complex in the rate-limiting stage and yield the products with regeneration of catalyst in the subsequent fast step. The reaction exhibits fractional order in hexacyanoferrate(II) and first-order unity each in oxidant and catalyst. The reaction constants involved in the mechanism are derived.     

Immobilization of (dd)heteronuclear hexacyanoferrates(II) in a gelatin matrix

The data concerning a possibility of the synthesis (dd)heteronuclear hexacyanoferrates(II) with (M¹)^II and (M²)^II ions (M¹, M² = Mn, Co, Ni, Cu, Zn, or Cd) due to the contact of M¹ ₂[Fe(CN)₆] immobilized in the gelatin matrix with aqueous solutions of M²Cl₂ chlorides, were systematized and generalized. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 8–17, January, 2008.     

Studies on mononuclear chelates derived from substituted Schiff-base ligands (part 6): synthesis and characterization of a new 3-ethoxysalicyliden- p -aminoacetophenoneoxime and its complexes with cobalt(II), nickel(II), copper(II) and zinc(II)

Schiff-base complexes of cobalt(II), nickel(II), copper(II) and, zinc(II) with 3-ethoxysalicyliden-p-aminoacetophenoneoxime (HL) were prepared and characterized on the basis of elemental analyses, IR, ¹H- and ¹³C-NMR, electronic spectra, magnetic susceptibility measurements, molar conductivity and thermogravimetric analyses (TGA). A tetrahedral geometry has been assigned to the complexes.     

Intercalation of hydrotalcites with hexacyanoferrate(II) and (III)—a thermoRaman spectroscopic study

Raman spectroscopy using a hot stage indicates that the intercalation of hexacyanoferrate(II) and (III) in the interlayer space of a Mg, Al hydrotalcites leads to layered solids where the intercalated species is both hexacyanoferrate(II) and (III). Raman spectroscopy shows that depending on the oxidation state of the initial hexacyanoferrate partial oxidation and reduction takes place upon intercalation. For the hexacyanoferrate(III) some partial reduction occurs during synthesis. The symmetry of the hexacyanoferrate decreases from O_h existing for the free anions to D_3d in the hexacyanoferrate interlayered hydrotalcite complexes. Hot stage Raman spectroscopy reveals the oxidation of the hexacyanoferrate(II) to hexacyanoferrate(III) in the hydrotalcite interlayer with the removal of the cyanide anions above 250 °C. Thermal treatment causes the loss of CN ions through the observation of a band at 2080 cm⁻¹. The hexacyanoferrate (III) interlayered Mg, Al hydrotalcites decomposes above 150 °C.     

Voltammetric and spectroscopic studies of water/formamide ratios in the production of the cerium (III) hexacyanoferrate (II) nanoparticles

The present study describes the simple and fast preparation of Cerium (III) hexacyanoferrate (II) (CeHCF) solid nanoparticles at three different water/formamide (%) ratios used as solvent (v/v) (100:0, 80:20, 0:100). CeHCF nanoparticles (Nps) were characterized by fourier transform infrared pectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), zeta potential and cyclic voltammetry (CV). Electrodes modified with CeHCF presented a well-defined redox pair with formal potential (E^o′) of approximately 0.29 V (vs. Ag/AgCl(sat) attributed to the Fe^{2 +}/Fe³⁺ redox pair in the presence of cerium (III)). The Nps in the three systems investigates, presents a random size distribution to different surface, where most were distributed between 20 and 160 nm. Considering the three investigated systems, only CeHCF-1 (100:0) was sensitive to L-dopamine, presenting a linear signal region as a function of L-dopamine concentrations, with a limit of detection (LD) of 0.125 mmol L⁻¹, limit of quantification (LQ) of 0.419 mmol L⁻¹ and amperometric sensitivity (S) of 148.16 μA mmol L⁻¹.     

Acridine-based ligands from cobalt(II) mediated rearrangement of diphenylamine-based starting materials

The synthesis and characterisation of two cobalt(II) complexes, [Co^IIL^Br-acrCl₂] (1a) and [Co^IIL^H-acrCl₂] (1b), with acridine head-units resulting from an unexpected ligand rearrangement from a diphenylamine head-unit, and the intended cobalt(II) complex, Co^IIL^Br-dpa(Cl)(H₂O) (2), are reported. Single crystals of the two dark green acridine-based cobalt(II) complexes, 1a and 1b, form in a one-pot reaction of cobalt(II) chloride, the chosen diphenylamine-2,2′-dicarboxaldehyde (Ia 4,4-′dibromo- or Ib unsubstituted), triethylamine and two equivalents of 2,4-dimethylaniline in acetonitrile, in 23% yield. In contrast, the intended diphenylamine-based complex was isolated in two steps: first isolation of the Schiff base ligand, then complexation with cobalt(II) chloride and deprotonation with potassium tert-butoxide, in methanol/dichloromethane, giving 2 as a bright yellow solid in 67% yield. All three complexes feature cobalt(II) centres, with N₂Cl₂ approximately tetrahedral coordination for 1a and 1b confirmed by single crystal structure determinations. It is proposed that after one imine ‘arm’ forms, cobalt(II) coordination facilitates the other aldehyde undergoing an intramolecular cyclisation to form the new heterocyclic acridine head-unit. The structures of both of the resulting acridine-based complexes, 1a and 1b, and that of the originally intended Schiff base ligand, HL^Br-dpa, were confirmed by single-crystal X-ray diffraction. These are the first examples of complexes of an acridine ligand of this type.     

Spectral and thermal studies of new Co(II) and Ni(II) hexaaza and octaaza macrocyclic complexes

The macrocyclic complexes of Co(II) and Ni(II) having chloride or thiocyanate ions in the axial position have been synthesized and characterized. These complexes are synthesised by the template condensation of o-phenylenediamine or 2,3-butanedionedihydrazone with the appropriate aldehydes in NH₄OH solution in the presence of the metal ions, Co(II) and Ni(II). The complexes were characterized by spectroscopic methods (IR, UV-Vis and ESR) and magnetic measurements as well as thermal analysis (TG and DTA). The results obtained are commensurate with the proposed formulae. Spectral studies indicate that these complexes have an octahedral structure. From conductivity measurements the complexes are non-electrolytes. The kinetic of the thermal decomposition of the complexes was studied and the thermodynamic parameters are reported.     

Regioselective 1,4-conjugate hydrocyanation of dienones using potassium hexacyanoferrate(II) as an eco-friendly cyanide source

A highly regioselective 1,4-conjugate hydrocyanation of dienones using potassium hexacyanoferrate(II) as an original eco-friendly cyanide source, benzoyl chloride as a promoter and potassium carbonate as a catalyst is described. This protocol has advantages of non-toxic cyanating agent, high regioselectivity, high yield, and simple work-up procedure.     

A thermal decomposition study on cobalt(II) complexes of 1,2-bis(IMINO-4'-antipyrinyl)ethane

The phenomenological, kinetic and mechanistic aspects of thermal decomposition of perchlorate, nitrate, chloride, bromide and iodide complexes of cobalt(II) with the Schiff base 1,2-bis(imino-4'-antipyrinyl)ethane (GA) have been studied by TG and DTG analyses. The kinetic parameters like the activation energy, pre-exponential factor and entropy of activation were calculated. The decomposition reactions follow 'random nucleation with one nucleus on each particle - Mampel model'. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cobalt(II)-8-mercaptoquinolines complexing in cobalt(II) hexacyanoferrate(II) gelatin-immobilized matrix materials

Complexing processes between Co^II and 8-mercaptoquinoline, or its various alkyl- and aryl-substituted derivatives, in contact with Co₂[Fe(CN)₆]-gelatin-immobilized matrix materials, with aqueous solutions of corresponding ligands, have been studied. When R² = Me or Ph, formation of Co^II chelates having a 1:2 metal ion/singly deprotonated ligand is observed, whereas when R² = H, formation of Co^III chelates having metal ion/singly deprotonated ligand 1:3 ratios occur.     

Ion pairing and the rate of the reaction between hexacyanoferrate(II) and octacyanotungstate(V) ions

The rate of the reaction Fe(CN) ₆ ^4– +W(CN) ₈ ^3– Fe(CN) ₆ ^3– +W(CN) ₈ ^4– in aqueous solution has been studied at various temperatures and ionic strengths, in the presence of Group IA cations. The results, combined with earlier work on the ion pairing of these compounds, give an indication of the number of cations present in the activated complex, a number which increases steadily in going from Li⁺ to Cs⁺ as the associated cations. Activation parameters for the reaction at various total [M⁺] are also evaluated.     

The synthesis and characterization of three new vic -dioximes and their nickel(II), copper(II) and cobalt(II) complexes

Three new vic-dioximes, [L¹H₂], N-(4-ethylphenyl)amino-1-acetyl-1-cyclohexenylglyoxime, [L²H₂], N-(4-butylphenyl)amino-1-acetyl-1-cyclohexenylglyoxime, and [L³H₂], N-(4-methoxyphenyl)amino-1-acetyl-1-cyclohexenylglyoxime were synthesized from 1-acetyl-1-cyclohexeneglyoxime and the corresponding substituted aromatic amines. Metal complexes of these ligands were also synthesized with Ni(II), Cu(II), and Co(II) salts. These new compounds (ligands and complexes) were characterized with FT–IR, magnetic susceptibility measurement, molar conductivity measurements, mass spectrometry measurements, thermal methods (e.g. thermal gravimetric analysis), ¹H NMR (Nuclear Magnetic Resonance) and ¹³C NMR spectral data and elemental analyses.     

Complexation in a 5-acylpyrimidine-4-thione—aliphatic diamine—metal(II) chloride system (M = Ni or Co). The molecular structure of <Emphasis Type="Italic">fac</Emphasis>-tris(5-acetyl-2,4-dimethylpyrimidine-6-thiolato)cobalt(III)

The reactions of 5-acylpyrimidine-4-thiones with aliphatic diamines in the presence of Ni^II and Co^II salts were studied. New Ni^II and Co^III complexes with ligands of the pyrimidinethione series were synthesized. The results of the reactions of 5-acetyl-6-methyl-2-phenylpyrimidine-4-thione and 5-acetyl-2,6-dimethylpyrimidine-4-thione with ethylenediamine or 1,3-diaminopropane in the presence of NiCl₂· 6H₂O or CoCl₂·6H₂O depend on (1) the nature of the substituent at position 2 of the pyrimidine ring, (2) the length of the polymethylene bridge between the nitrogen atoms in the diamine molecule, (3) the nature of complex-forming metal, and (4) the pyrimidinethione: diamine ratio. The resulting complexes were studied by electrochemical methods. The mechanism of electrooxidation and electro-reduction of 5-acylpyrimidine-2-thiones and related nickel and cobalt complexes was proposed. The structures of the complexes were investigated by NMR, UV-Vis spectroscopy, and IR spectroscopy and mass spectrometry. The molecular structure of fac-tris(5-acetyl-2,4-dimethylpyrimidine-6-thiolato)cobalt(III) was established by X-ray diffraction. According to semiempirical quantum-chemical calculations by the PM3(tm) method, both the highest occupied and lowest unoccupied molecular orbitals in the molecules of the compounds under study have a π symmetry and are localized predominantly on the ligand fragments. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2666–2678, December, 2005.     

Some new cobalt(II) complexes: Synthesis,characterization and thermal studies

Cobalt(II) complexes of tetradentate Schiff bases of the type CoL [H₂L=C₂₀H₁₆N₂O₂ (H₂dsp), C₂₁H₁₈N₂O₂ (H₂dst), C₂₀H₁₅N₃O₄ (H₂ndsp) and C₁₆H₁₆N₂O₂ (H₂salen)] have been synthesized and characterized by UV-visible, IR, and magnetic studies. Various thermodynamic parameters have been calculated for the decomposition step using TG/DTA. C₂₀H₁₄N₂O₂Co complex has the minimum and C₁₆H₁₄N₂O₂Co complex has the maximum activation energy.This revised version was published online in November 2005 with corrections to the Cover Date.     

Organometallic-mediated radical polymerization using well-defined Schiff base cobalt(II) complexes

Abstract

A series of new cobalt(II) complexes of Schiff base derived from salicylaldehyde and different cycloalkylamines (cycloalkyl?=?cyclopentyl-1a, cyclohexyl-1b, and cycloheptyl-1c) was synthesized: [Co(CyPen-Salicyl)₂] (2a), [Co(CyHex-Salicyl)₂] (2b), and [Co(CyHep-Salicyl)₂] (2c). The bis(phenoxyiminato)Co(II) complexes (2a-2c) have been fully characterized by FTIR and UV–vis spectroscopy, elemental analysis, cyclic voltammetry, computational methods, and two of the complexes were further studied by single crystal X-ray crystallography. The X-ray structure analysis of 2a-b shows that the geometry around the metal atom is a distorted tetrahedron, confirming the spectroscopic data. Electrochemical studies suggest that the redox potential of 2a-2c are sensitive to the substituent group, decreasing in order cyclopentyl?>?cyclohexyl?>?cycloheptyl. Complexes 2a-2c were used as controlling agents for the polymerization of vinyl acetate (VAc) initiated by AIBN, according to a cobalt-mediated radical polymerization (CMRP) mechanism. The VAc polymerization mediated by 2a-2c suggests that the level of control can be slightly tuned by the substitution of the cycloalkyl group on the Schiff base ligand. Complex 2b showed the smaller discrepancy between observed and calculated molecular weight, and narrower molecular weight distribution.     

Voltammetric determination of isoprenaline in pharmaceutical preparations using a copper(II) hexacyanoferrate(III) modified carbon paste electrode

The electroanalytical determination of isoprenaline in pharmaceutical preparations of a homemade carbon paste electrode modified with copper(II) hexacyanoferrate(III) (CuHCF) was studied by cyclic voltammetry. Several parameters were studied for the optimization of the sensor such as electrode composition, electrolytic solution, pH effect, potential scan rate and interferences in potential. The optimum conditions were found in an electrode composition (in mass) of 15% CuHCF, 60% graphite and 25% mineral oil in 0.5 mol l⁻¹ acetate buffer solution at pH 6.0. The analytical curve for isoprenaline was linear in the concentration range from 1.96×10⁻⁴ to 1.07×10⁻³ mol l⁻¹ with a detection limit of 8.0×10⁻⁵ mol l⁻¹. The relative standard deviation was 1.2% for 1.96×10⁻⁴ mol l⁻¹ isoprenaline solution (n=5). The procedure was successfully applied to the determination of isoprenaline in pharmaceutical preparations; the CuHCF modified carbon paste electrode gave comparable results to those results obtained using a UV spectrophotometric method.     

Co(II)Schiff碱配合物的合成、氧合反应热力学及热分解动力学的研究

合成了两种新的钴(II)schiff碱配合物水杨醛L-甲硫氨酸-水合钴(II)(1), 邻香兰素L-甲硫氨酸-水合钴(II)(2)。通过元素分析、红外光谱、热分析等测试手段研究了配合物的性质, 并确定了配合物的组成。用气体吸收装置测定配合物在乙腈溶液中不同温度下的饱和吸氧量, 求得氧合反应的平衡常数及热力学参数, 同时探讨了温度和配体结构对配合物氧合性能的影响。用TG-DTG法研究了配合物的热稳定性及非等温热分解动力学, 并采用积分法和微分法相结合的方法,推断了两种配合物的第一步热分解反应机理, 得到了热分解反应动力学参数及其动力学方程。     

Syntheses and crystal structures of two 2D coordination polymers of cobalt(II) and nickel(II) with the Malonate Dianion Ligand

Two 2D complexes, [Co(mal)(phen)(H₂O)₂] (1) and [Ni(mal)(phen)(H₂O)₂] (2) (mal?=?malonate dianion; phen?=?1,10-phenanthroline), have been synthesized by the reaction of Co(ClO₄)₂·6H₂O and Ni(ClO₄)₂·6H₂O with disodium malonate and 1,10-phenanthroline in MeOH/H₂O solution. Their crystal structures have been determined by X-ray diffraction. The structures of Complexes 1 and 2 show that each metal ion is coordinated by one 1,10-phenanthroline, two water molecules and a malonate ligand forming a distorted octahedral environment and each mononuclear fragment forms a 2D supramolecular network through H-bonding interactions.