Bis­[bis­(diethyl­enetri­amine)­zinc(II)] hexa­cyano­ferrate tetrahydrate

In the crystal structure of the title compound, [Zn(C₄H₁₃N₃)₂]₂[Fe(CN)₆]·4H₂O, the asymmetric unit is formed by a [Zn(dien)₂]²⁺ cation (dien = diethyl­enetri­amine, NH₂CH₂CH₂NHCH₂CH₂NH₂), water mol­ecules and half of the [Fe(CN)₆]^4? anion which is related by inversion symmetry through the Fe atom. The geometry around the Zn and Fe atoms is distorted octahedral and octahedral, respectively. Intramolecular O—H?O hydrogen bonds involving the water mol­ecules, and intermolecular O—H?N hydrogen bonds involving the water mol­ecules and the anions, result in an infinite chain. Intramolecular O—H?O and N—H?N, and intermolecular O—H?N, N—H?O and N—H?N hydrogen bonds form a three‐dimensional framework.     

Synthesis,crystal structures and magnetic properties of a series of new cyano-bridged complexes derived from templates [Ni(CN)4]2− and [Co(III)(CN)6]3−

Three new cyano-bridged complexes 1 [Ni(tn)₂Ni(CN)₄] (tn?=?1,3-diaminopropane), 2 [Cu^II(dipn)Ni^II(CN)₄], and 3 [Cu(dipn)]₆[Co(CN)₆]₄?·?4H₂O (dipn?=?dipropylenetriamine) have been assembled by the templates [Ni(CN)₄]^2? and [Co(CN)₆]^3?. 1 consists of a one-dimensional linear chain–Ni(tn)₂–NC–Ni(CN)₂–CN–Ni(tn)_2? in which the Ni(II) centers are linked by two CN groups. One 1-D zigzag chain of 2 is formed with–Ni(2)–C–N–Cu(1)–N–C–linkages. A 2D structure of 3 is formed by an alternate array of [Co(CN)₆]^3? and [Co][Cu₆] units. For 1, there is an overall weak antiferromagnetic interaction between Ni(II) ions through the–NC–Ni–CN–bridges of the diamagnetic [Ni(CN)₄]^2? anions. 2 exhibits a weak antiferromagnetic exchange interaction between copper(II) ions mediated by [Ni(CN)₄]^2? diamagnetic bridges. Complex 3 exhibits a weak ferromagnetic interaction between nearest Cu^II and Cu^II atoms through–NC–Co–CN–bridges.     

Synthesis,crystal structure,and magnetic properties of an octacyanometallate-based Ni/Mo bimetallic complex with the diamond topological network

Reaction of [NiL]²⁺ (L = 3,10-diethyl-1,3,5,8,10,12-hexaazacyclotetradecane) with [Mo(CN)₈]^4? leads to a new Ni₂Mo complex [Ni(L)]₂[Mo(CN)₈] · 8H₂O (1), which displays a 3-D diamond topological network. Magnetic study indicates a combination of zero-field splitting of Ni²⁺ in an axially distorted octahedral coordination and weak antiferromagnetic interactions between Ni²⁺ centers through diamagnetic [Mo(CN)₈]^4? bridges.     

Studies in nickel(IV) chemistry. Electron transfer kinetics of the reaction between tris(dimethylglyoximato)nickelate(IV) and hexacyanoferrate(II) in aqueous medium

The kinetics of electron transfer from hexacyanoferrate(II) to tris(dimethylglyoximato)-nickelate(IV), Ni(dmg)₃^2?, to produce Fe(CN)₆^3? and Ni(dmgH)₂, follows a pseudo-first-order disappearance in the Ni(IV). The pseudo-first-order rate constants k_obs are linearly dependent on [Fe(CN)₆^4?]₀ in a fiftyfold range of 2 × 10^?4?1 × 10^?2M, and the average values of k_obs/[Fe(CN)₆^4?]₀ range from 194M^?1·s^?1 at pH = 5.20 to 0.2M^?1·s^?1 at pH = 9.07 in aqueous medium at 35°C and μ = 0.57M. Results are interpreted in terms of a probable mechanism involving rate-determining outer sphere one-electron transfer steps from the reductant and one-protonated reductant species to the unprotonated and one-protonated Ni(IV) species present in solution. The more electrophilic one-protonated reductant species apparently reacts several orders of magnitude faster than the unprotonated one.     

Synthesis,crystal structure and catalytic performance of bis (imino)pyridyl nickel complexes

Two new Ni(II) complexes of 2,6-bis[1-(2,6-diethylphenylimino)ethyl]pyridine (L¹), 2,6-bis[1-(4-methylphenylimino)ethyl]pyridine (L² ) have been synthesized and structurally characterized. Complex Ni(L¹)Cl₂?·?CH₃CN (1), exhibits a distorted trigonal bipyramidal geometry, whereas complex Ni(L¹)(CH₃CN)Cl₂ (2), is six-coordinate with a geometry that can best be described as distorted octahedral. The catalytic activities of complexes 1, 2, Ni{2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine} Cl₂?·?CH₃CN (3), and Ni{2,6-bis[1-(2,6-dimethylphenylimino) ethyl]pyridine}Cl₂?·?CH₃CN (4), for ethylene polymerization were studied under activation with MAO.     

Temperature Influence on the Formation of Selenidoantimonates: Solvothermal Syntheses,Crystal Structures and Thermal Properties of [Ni(dien)2]2Sb2Se6, [Mn(dien)2]2(SbSe4)(Cl), [Co(dien)2]2(SbSe4)(Br), and [Co(dien)2]3(SbSe4)2

New selenidoantimonats [Ni(dien)₂]₂Sb₂Se₆ ( 1 ), [Mn(dien)₂]₂(SbSe₄)(Cl) ( 2 ), [Co(dien)₂]₂(SbSe₄)(Br) ( 3 ), and [Co(dien)₂]₃(SbSe₄)₂ ( 4 ) (dien = diethylenetriamine) were solvothermally synthesized in dien solvent at 180 °C. The crystal structure of 1 consists of two octahedral [Ni(dien)₂]²⁺ cations and a mixed‐valent [Sb₂Se₆]^4? anion. The isolated [Sb₂Se₆]^4? anion is formed by a Sb^IIISe₃ trigonal pyramid and a Sb^VSe₄ tetrahedron sharing a common corner. 2 and 3 are composed of octahedral [M(dien)₂]²⁺ cations, tetrahedral [SbSe₄]^3? anions and halide ions forming an extended network through hydrogen‐bonding interactions. In 4 the [Co(1)(dien)₂]²⁺, [Co(2)(dien)₂]²⁺ and [SbSe₄]^3? ions form layered structures via N–H···Se hydrogen bonds. The [Co(3)(dien)₂]²⁺ ion is located between the layers, and interacts with the layers by N–H···Se bonds. The synthesis and solid state structural studies on the title compounds show that the higher reaction temperature is helpful for the formation of selenidoantimonate(V) compounds in the synthesis of selenidoantimonate from the M²⁺/Sb/Se/dien system. 1 – 4 start to decompose at temperature about 210 °C in N₂ atmosphere. They lose dien ligands at a wide temperature range of 210–450 °C with multisteps for 1 – 3 and a single step for 4 .     

Tetracyanometallates with Complex Dien Cations: [Ni(dien)2][Ni(CN)4]·2H2O and [Ni(dien)2][Pd(CN)4]

The crystal structures of two square tetracyanocomplexes were determined. [Ni(dien)₂][Ni(CN)₄]·2H₂O (NDNCH) and [Ni‐(dien)₂][Pd(CN)₄] (NDPC) (dien = diethylene triamine) exhibit ionic structures consisting of mer‐[Ni(dien)₂]²⁺ cations and [Ni(CN)₄]^2‐ or [Pd(CN)₄]^2‐ anions, respectively. Moreover, the structure of NDNCH is completed by two water molecules of crystallisation. In both compounds hydrogen bonds contribute to the stabilisation of the structure. NDNCH dehydrates on air quickly yielding anhydrous [Ni(dien)₂][Ni(CN)₄] (NDNC). Its thermal decomposition proceeds in a complicated process followed by aerial oxidation of metallic nickel to NiO.     

Quantum chemical studies of Lindqvist-type polyoxometalates containing late 3d transition metals ([(py)MIIW5O18]4? (M?=?Fe, Co, Ni)): MII�CN bonding and second-order nonlinear optical properties

The electronic and nonlinear optical (NLO) properties of Lindqvist-type tungstate containing late 3d transition metals [(py)MW₅O₁₈]^4? (M?=?Fe, Co, Ni) have been systematically investigated using density functional theory (DFT) method. The character of M?CN bond is analyzed using natural bond orbital methods. The first hyperpolarizabilities of [(py)MW₅O₁₈]^4? anions have been investigated by Coulomb-attenuating method (CAM-B3LYP). The NLO properties of [(py)MW₅O₁₈]^4? with different spin states are also studied. The results show that the static second-order polarizability (?? ₀) of [(py)⁵FeW₅O₁₈]^4? (Fe?=?quintet state) is 525.10?×?10^?30 esu, which is larger than those of [(py)⁴CoW₅O₁₈]^4? (?? ₀?=?120.72?×?10^?30 esu) and [(py)³NiW₅O₁₈]^4? (?? ₀?=?30.45?×?10^?30 esu) anions. Time-dependent DFT results reveal that the substituted transition metals-to-pyridine charge transfer may be responsible for the NLO properties of this kind of polyoxometalates.     

Synthesis,Crystal Structure and Nonlinear Optical Properties of a new cluster compound: MoS4Cu3(PyPPh2)3Cl

Reaction of [NH₄]₂[MoS₄], CuCl and PyPPh₂ in the solid state produces a cube-like cluster. The cluster crystallizes in the orthorhombic space group P2₁2₁2₁ with four formula units in a cell of dimensions a = 12.8980(10) , b = 17.6820(10), c = 22.665(2) Å. Anisotropic refinement for all nonhydrogen atoms yielded the values R = 0.0397 and R _w = 0.1185 for 8803 observed reflections. The structure is built up from three [Cu(Ph₂PPy)]⁺ units bridged by MoS^2? ₄ to form a tetranuclear symmetrical cube-like molecule. Investigation of the third-order optical nonlinear value showed that it exhibits a considerable nonlinear absorptive and self-defocusing effect with α₂ = 1.3 × 10^?11 m w^?1 and n ₂ = ? 3.2 × 10^?18 m² w^?1 in a 1.5 × 10^?4 M DMF solution.     

Synthesis,crystal structures,and magnetic properties of three K[M(bpb)(CN)2]-based trinuclear sandwich-like heterobimetallic M(III)–Ni(II) (M = Fe,Cr, Co) complexes

Three trinuclear sandwich-type cyanide-bridged M^III–Ni^II complexes, {[Ni(cyclm)[Fe(bpb)(CN)₂]₂}·8H₂O (1), {[Ni(cyclm)[Cr(bpb)(CN)₂]₂}·2H₂O (2), and {[Ni(cyclm)[Co(bpb)(CN)₂]₂}·CH₃OH·2H₂O (3) (cyclm?=?1,4,8,11-tetraazacyclotetradecane), have been synthesized using K[M(bpb)(CN)₂] (M?=?Fe, Cr, Co; bpb?=?1,2-bis(pyridine-2-carboxamido)benzenate) as building block and one Ni(II) compound containing a 14-membered macrocycle ring as assembling segment. All the complexes have been characterized by elemental analysis, IR spectroscopy, and X-ray structure determination. Single X-ray diffraction analysis shows similar sandwich-like structures, in which the two cyanide-containing building blocks are monodentate through one of their two cyanides, coordinated face to face to the central Ni(II). Investigation of the magnetic properties of 1 and 2 reveals ferromagnetic magnetic coupling between the neighboring Fe(III)/Cr(III) and Ni(II) through the bridging cyanide. A best-fit to the magnetic susceptibilities of 1 and 2 based on the trinuclear M₂Ni model leads to magnetic coupling constants J?=?5.47(1)?cm^?1 for 1 and J?=?6.37(2)?cm^?1 for 2.     

Anionische Nickel-Pseudohalogenid-Komplexe der Typen [Ni{N(CN)2}3]− und [Ni{N(CN)2}2(NCS)2]2−

Anionie Nickel Pseudohalide Complexes of the Types [Ni{N(CN)₂}₃]^? and [Ni{N(CN)₂}₂(NCS)₂]^2? The preparation of a new type of anionic pseudohalide complexes of nickel [Ni{N(CN)₂}₃]^? and of mixed thiocyanate-dicyanamide complexes [Ni{N(CN)₂}₂(NCS)₂]^2? is reported. The structures of the complexes are discussed on the basis of IR- and magnetic measurements. The new compounds are representing polymer octahedral complexes with a bridging function of the dicyanamide ligands.     

Cu2(dien)2Ag5(CN)9 containing the one‐dimensional polymeric cation [Cu(dien)Ag(CN)2]nn+ and the unusual [Ag2(CN)3]− anion (dien is diethylenetriamine)

From the 1:1 system of [Cu(dien)₂](NO₃)₂ and K[Ag(CN)₂] in water (dien is diethyl­enetri­amine, C₄H₁₃N₃), the novel compound catena‐poly­[bis­[[μ‐cyano‐1:2κ²C:N‐diethyl­enetri­amine‐2κ³N‐copper(II)silver(I)]‐μ‐cyano‐1:2′κ²C:N] di­cyano­silver(I) tri­cyanodisilver(I)], [CuAg(CN)₂(dien)]₂[Ag(CN)₂][Ag₂(CN)₃], has been isolated. The structure is formed from positively charged [–Cu(dien)–NC–Ag–CN–]_nⁿ⁺ chains and two isolated centrosymmetric [Ag(CN)₂]^? and [Ag₂(CN)₃]^? anions. In the cationic chains, the Cu atoms are linked by bridging di­cyano­argentate groups, and the deformed square‐pyramidal coordination polyhedron of the Cu^II cation is formed from a tridentate chelate‐like bonded dien ligand and two N‐bonded bridging cyano groups. One of the bridging cyano groups occupies the apical (ap) position [mean Cu—­N_eq = 2.02 (2) Å, and Cu—N_ap = 2.170 (3) Å; eq is equatorial]. Short argentophilic interactions in the range 3.16–­3.30 Å are present in the crystal structure.     

Electrochemical Responses and Sensitivities of Films Based on Multi-Walled Carbon Nanotubes in Aqueous Solutions

Novel films consisting of multi-walled carbon nanotubes (MWCNTs) were fabricated by means of chemical vapor deposition with decomposition of either acetonitrile (ACN) or benzene (BZ) using ferrocene as catalyst. The electrochemical responses of MWCNT-based films towards the ferrocyanide/ferricyanide, [Fe(CN)₆]^3?/4? redox couple were probed by means of cyclic voltammetry and electrochemical impedance spectroscopy at 25.0?±?0.5?°C. Both MWCNT-based films exhibit Nernstian response towards [Fe(CN)₆]^3?/4? with some slight kinetic differences. Namely, heterogeneous electron transfer rate constants lying in ranges of 2.69?×?10^?2?C1.7?×?10^?3 and 9.0?×?10^?3?C2.6?×?10^?3?cm·s^?1 were obtained at v?=?0.05?V·s^?1 for MWCNT_ACN and MWCNT_BZ, respectively. The detection limit of MWCNT_ACN, estimated to be about 4.70?×?10^?7?mol·L^?1 at v?=?0.05?V·s^?1, tends to become slightly poorer with the increase of the scan rate, namely at v?=?0.10?V·s^?1 the detection limit of 1.70?×?10^?6?mol·L^?1 was determined. Slightly poorer response ability was exhibited by MWCNT_BZ; specifically the detection limits of 1.57?×?10^?6 and 4.35?×?10^?6?mol·L^?1 were determined at v?=?0.05 and v?=?0.10?V·s^?1, respectively. The sensitivities of MWCNT_ACN and MWCNT_BZ towards [Fe(CN)₆]^3?/4? were determined as 1.60?×?10^?7 and 1.51?×?10^?7?A·L·mol^?1·cm^?2, respectively. The excellent electrochemical performance of MWCNT_ACN is attributed to the presence of incorporated nitrogen in the nanotube??s structure.     

The kinetics and mechanism of oxidation of hexacyanoferrate(II) by periodate ion in highly alkaline aqueous medium

The oxidation of hexacyanoferrate(II) by periodate ion has been studied spectrophotometrically by registering an increase in absorbance at 420 nm (λ_max of yellow colored [Fe(CN)₆ ^3?] complex under pseudo first-order conditions by taking excess of [IO₄ ^?] over [Fe(CN)₆ ^4?]. The reaction conditions were: pH = 9.5 ± 0.02, I = 0.1 M (NaCl) and Temp. = 25 ± 0.1 °C. The reaction exhibited first-order dependence on each [IO₄ ^?] and [Fe(CN)₆ ^4?]. The effects of variations of pH, ionic strength and temperature were also studied. The experimental observations revealed that the periodate ion exists in its protonated forms viz. [H₂IO₆]^3? and [H₃IO₆]^2? while [Fe(CN)₆]^4? is present in its deprotonated form throughout the pH region selected for the present study. It has also been observed that deprotonated form of [Fe(CN)₆ ^4?] and protonated forms of periodate ion are the most reactive species towards oxidation of [Fe(CN)₆ ^4?]. The repetitive spectral scan is provided as an evidence to prove the conversion of [Fe(CN)₆ ^4?] to [Fe(CN)₆ ^3?] in the present reaction. The activation parameters have also been computed using the Eyring’s plot and found to be, ΔH? = 51.53 ± 0.06 kJ mol^?1, ΔS? = ?97.12 ± 1.57 J K^?1 mol^?1 and provided in support of a most plausible mechanistic scheme for the reaction under study.     

Effects of alkyltrimethylammonium bromide surfactants on the kinetics of the oxidation of tris(1,10-phenanthroline)iron(II) by azido-pentacyanocobaltate(III) complex

The redox reaction between tris(1,10-phenanthroline)iron(II), [Fe(phen)₃]²⁺, and azido-pentacyanocobaltate(III), [Co(CN)₅N₃]^3? was investigated in three cationic surfactants: dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB) in the presence of 0.1?M NaCl at 35°C. Second-order rate constant in the absence and presence of surfactant, k_w and k_ψ, respectively, were obtained in the concentration ranges DTAB?=?0???4.667?×?10^?4?mol?dm^?3, TTAB?=?0–9.364?×?10^?5?mol?dm^?3, CTAB?=?0???6.220?×?10^?5?mol?dm^?3. Electron transfer rate was inhibited by the surfactants with premicelllar activity. Inhibition factors, k_w/k_ψ followed the trend CTAB?>?TTAB?>?DTAB with respect to the surfactant concentrations used. The magnitudes of the binding constants obtained suggest significant electrostatic and hydrophobic interactions. Activation parameters ΔH^≠, ΔS^≠, and E_a have larger positive values in the presence of surfactants than in surfactant-free medium. The electron transfer is proposed to proceed via outer-sphere mechanism in the presence of the surfactants.     

Synthesis,structure, and photoluminescence of a (4,6)-connected Cu(I)–CN–triazolate framework built with a unique heptanuclear hybrid cluster

A 3-D Cu(I)–CN–triazolate hybrid coordination polymer, {Cu₉(NH₂-BPT)₂(BPT)₂(CN)₇}_n (1) (NH₂-BPT = 4-amino-3,5-bis(3-pyridyl)-1,2,4-triazole, BPT = 3,5-bis(3-pyridyl)-1,2,4-triazole), has been synthesized via self-assembly of NH₂-BPT, CuCN, and K₃Fe(CN)₆ under hydrothermal conditions. Single-crystal X-ray diffraction data show that four of the five independent copper centers in 1 have a three-coordinated trigonal coordination geometry, and the remaining copper center has a two-coordinated linear geometry. Three Cu ions are linked by one cisoid-BPT and two CN^? to form a 16-membered ring subunit, which is joined by the two-coordinate copper center via the triazole N(4)-position to generate an unprecedented [Cu₇(BPT)₂(CN)₄] hybrid heptanuclear cluster. Each heptanuclear motif is linked to two adjacent [Cu₇] clusters through four CN^? anions, and further to four [Cu–CN–Cu] binuclear clusters through two transoid-NH₂-BPT ligands. Each of these [Cu–CN–Cu] units is linked to four neighboring heptanuclear motifs. The overall geometry is a 3-D (4,6)-connected topological framework with Schläfli symbol of (4^4?×?6²)(4^4?×?6^10?×?8). Compound 1 also exhibits high thermal stability and strong green fluorescence emission at 536?nm in the solid state.     

Synthesis,structures and magnetic properties of nickel bis (dithiolene) complexes with [Fe(qsal)2]+

Two new compounds containing the possible Fe(III) spin-crossover cation, [Fe(qsal)₂]⁺ (qsalH = N-(8-quinolyl)salicylaldimine), and nickel bis(dithiolene) anions have been synthesized. Both are 1 : 1 salts [Fe(qsal)₂][Ni(dddt)₂] · CH₃CN · CH₃OH (1) and [Fe(qsal)₂][Ni(pddt)₂] (2) (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate; pddt = 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate). They have been characterized by X-ray crystal structure determination, elemental analysis, UV-Vis spectra and magnetic susceptibility measurements. The UV–Vis spectra are dominated by [Ni(L)₂]^? (1, L = dddt; 2, L = pddt). Magnetic studies show antiferromagnetic interaction in 1 from intermolecular S···S contacts and π–π stacking interactions, while the antiferromagnetic interaction in 2 is very weak.     

Kinetic determination of hexacyanoferrates by their inhibition of an oscillating chemical reaction

A method for the kinetic determination of traces of hexacyanoferrate based on an oscillating chemical reaction is presented. In a Belousov-Zhabotinskii reaction system, by using a bromide ion-selective electrode, the amplitude decrease of the potentiometric oscillation is linearly proportional to the concentration of Fe(CN)^3?₆ [or Fe(CN)^4?₆] in the range 7 × 10^?8?5 × 10^?6 M. The relative standard deviation for 1 × 10^?6 M Fe(CN)^3?₆ is 2.7% (n = 6). Cyclic voltammetry was applied to study the mechanism of the proposed system. The procedure was utilized to determine hexacyanoferrates in silver plating and photographic solutions.     

The silver(I)‐catalyzed exchange of coordinated cyanide in hexacyanoferrate(II) by phenylhydrazine in aqueous medium

The [Ag]⁺‐catalyzed exchange of coordinated cyanide in [Fe(CN)₆]^4? by phenylhydrazine (PhNHNH₂) has been studied spectrophotometrically at 488 nm by monitoring increase in the absorbance for the formation of cherry red colored complex [Fe(CN)₅PhNHNH₂]^3?. The other reaction conditions were pH 2.80±,0.02, temperature = 30.0 ± 0.1^°C, and ionic strength (I) = 0.02 M (KNO₃). The reaction was followed as a function of pH, ionic strength, temperature, [Fe(CN)^4?₆], [PhNHNH₂], [Ag⁺] by varying one variable at a time. The initial rates were evaluated for each variation using the plane mirror method. The initial rates evaluated as a function of [Fe(CN)^4?₆] clearly indicate that the initial rate increases with the increase in [Fe(CN)^4?₆] and finally reaches to a limiting value when [Fe(CN)^4?₆]/[AgNO₃] ? 1000. It indicates the formation of a strong adduct between [Fe(CN)₆]^4? and AgNO₃ prior to the abstraction of CN^?. The variation in initial rates with [PhNHNH₂] also showed limiting values at [Fe(CN)^4?₆]/[PhNHNH₂] ? 8.30. The complex behavior due to pH and [Ag⁺] variations on the rate has been explained in detail. The composition of the final reaction product [Fe(CN)₅PhNHNH₂] formed during the course of reaction has been found to be 1:1 using the mole ratio method. The evaluated values of activation parameters for the catalyzed reaction are E_a = 53.85 kJ mol^?1, Δ H^≠, = 51.33 kJ mol^?1, and Δ S^≠ = ?134.63 J K^?1 mol^?1, which suggest an interchange dissociative mechanism. A most plausible mechanistic scheme has been proposed based on the experimental observations. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 447–456, 2007