New oscillating chemical reactions involving copper and nickel tetraazamacrocyclic complexes

Copper and nickel complexes with tetraazamacrocyclic ligands are shown to act as catalysts in Belousov-Zhabotinskii oscillating reactions. New oscillating reactions, viz. the oxidation of unsaturated macrocyclic complexes of copper and nickel by bromate-ions, have been discovered.

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Electron transfer reactions of nickel(III) and nickel(IV) complexes

This review narrates the electron transfer reactions of various nickel(III) and nickel(IV) complexes reported during the period 1981 until today. The reactions have been categorized mainly with respect to the type of nickel complexes. The reactivity of nickel(III) complexes of macrocycles, 2,2′-bipyridyl and 1,10-phenanthroline, peptides and oxime–imine, and of nickel(IV) complexes derived from oxime–imine, oxime and miscellaneous ligands with various organic and inorganic electron donors have been included. Kinetic and mechanistic features associated with such interactions have been duly analyzed. The relevance of Marcus cross-relation equations in the delineation of the electron transfer paths has also been critically discussed.     

Halogen substituted quadridentate schiff bases,their nickel(II) and cobalt(III) complexes

Summary Electrophilic substitutions have been performed on the methyne carbon of NiL and [CoL,2py]ClO₄ [L=N,N-bis(acetylacetone) ethylenediiminato-]. The effects of substituents (H, Cl, Br and I) on the electron distribution within the cobalt(III) complexes have been investigated through¹H and¹³C n.m.r., i.r. spectroscopy and half-wave potential measurements     

Unsymmetrical β-diketones, monothio-β-diketones and their nickel(II) and cobalt(III) complexes

Summary Unsymmetrically substituted β-diketones, RCOCH₂COR′ (R and R′ = aryl) have been synthesized and used to prepare their monothio-β-diketone derivatives. Because of the similar basicities of the carbonyl oxygen due to the electronic effects of the R and R′ groups, a mixture of the monothio-β-diketones, RCSCH₂COR′ and R′CSCH₂-COR, is formed. Several of the monothio-β-diketones have been used to prepare their corresponding Ni^II and Co^II complexes. Mass spectral and ¹³C-n.m.r. data are used to confirm the formation of isomers of the monothio-β-diketonate ligands and their metal complexes.     

Synthesis and properties of cyano-bridged nickel(II)-iron(III) complexes

Summary Four kinds of novel CN-bridged Ni^II-Fe^III complexes, [NiLn(NC)Fe(CN)₅] ^–, have been synthesized and characterized by elemental analysis, i.r. and u.v.-vis. spectral analysis, and magnetic moments. The formation of cyanide bridges is evident from the i.r. and u.v.-vis. spectra by the appearance of v(CN) shifts and changes in _max with respect to the mononuclear parent complex [Fe(CN)₆]^3–. The magnetic properties indicate the existence of magnetic spin interactions between Ni^II and Fe^III through the cyanide bridge.     

Mechanism of oxidation of alanine by chloroaurate(III) complexes in acid medium: Kinetics of the rate processes

The kinetics of the oxidation of alanine by chloroaurate(III) complexes in acetate buffer medium has been investigated. The major oxidation product of alanine has been identified as acetaldehyde by ¹H NMR spectroscopy. Under the experimental conditions, AuCl and AuCl₃(OH)^? are the effective oxidizing species of gold(III). The reaction is first order with respect to Au(III) as well as alanine. The effects of H⁺ and Cl^? on the second‐order rate constant k₂′ have been analyzed, and accordingly the rate law has been deduced: k₂′ = (k₁[H⁺][Cl^?] + k₃K₄K₅)/(K₄K₅ + [H⁺][Cl^?]). Increasing dielectric constant of the medium has an accelerating effect on the reaction rate. Activation parameters associated with the overall reaction have been calculated. A mechanism involving the two effective oxidizing species of gold(III) and zwitterionic species of alanine, consistent with the rate law, has been proposed. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 473–482, 2009     

Kinetics and mechanism of pentacyanohydroxoferrate(III) formation from mono(aminocarboxylato)iron(III) complexes

Summary The kinetics and mechanism of the system: [FeL(OH)]^2–n + 5 CN^– [Fe(CN)₅(OH)]^3– + L^n–, where L=DTPA or HEDTA, have been investigated at pH= 10.5±0.2, I=0.25 M and t=25±0.1 C.As in the reaction of [FeEDTA(OH)]^2–, the formation of [Fe(CN)₅(OH)]^3– through the formation of mixed ligand complex intermediates of the type [FeL(OH)(CN)_x]^2–n–x, is proposed. The reactions were found to consist of three observable stages. The first involves the formation of [Fe(CN)₅(OH)]^3–, the second is the conversion of [Fe(CN)₅(OH)]^3– into [Fe(CN)₆]^3– and the third is the reduction of [Fe(CN)₆]^3– to [Fe(CN)₆]^4– by oxidation of L^n– The first reaction exhibits a variable order dependence on the concentration of cyanide, ranging from one at high cyanide concentration to three at low concentration. The transition between [FeL(OH)]^2–n and [Fe(CN)₅(OH)]^3– is kinetically controlled by the presence of four cyanide ions around the central iron atom in the rate determining step. The second reaction shows first order dependence on the concentration of [Fe(CN)₅(OH)]^3– as well as on cyanide, while the third reaction follows overall second order kinetics; first order each in [Fe(CN)₆]^3– and L^n–, released in the reaction. The reaction rate is highly dependent on hydroxide ion concentration.The reverse reaction between [Fe(CN)₅(OH)]^3– and L^n– showed an inverse first order dependence on cyanide concentration along with first order dependence each on [Fe(CN)_5– (OH)]^3– and L^n–. A five step mechanism is proposed for the first stage of the above two systems.     

Heterogeneous reactions of solid nickel(II) complexes,III

The thermal decompositions of solid complexes of the type Ni(NCS)₂L₂ (L = pyridine,α-picoline,β-picoline, 2,6-lutidine, and quinoline) were studied by means of the derivatograph. It was found that the decompositions of complexes with pyridine,α-picoline, 2,6-lutidine, and quinoline (the pseudo-octahedral complex) are onestep processes, and those of complexes withβ-picoline and quinoline (the squareplanar complex) consist of two steps. Diffuse reflectance spectra were recorded to elucidate the structures of the decomposition intermediates. The reasons for the different stoichiometries of decomposition for complexes of the same type are discussed.     

Kinetics of formation of Fe(III) complexes in aqueous DMSO

Spectrophotometric observations have been used to study equilibria and temperature jump relaxation associated with formation of Fe(III) complexes in aqueous DMSO in the presence of SCN⁻. The [SCN⁻] dependent relaxation observed at 315 nm could be assigned to the formation of Fe DMSO³⁺, Fe DMSO OH²⁺, Fe DMSO SCN²⁺ and Fe DMSO SCN OH⁺ from Fe²⁺ and Fe OH²⁺. The relaxation observed at 450 nm could be assigned to the formation of Fe SCN²⁺ by paths similar to that in aqueous solutions and a pH dependent path in which the rate determining step is the displacement of DMSO from Fe DMSO SCN OH⁺ by H₂O. The rate constants suggest that coordination by a DMSO instead of a H₂O has the effect of labilising the other H₂O coordinated to Fe OH²⁺. The observed decrease in relaxation rates with increase in [DMSO] have been explained as dominantly due to the reduction in the acid dissociation constant K_H associated with the aquocomplex of Fe(III).     

Kinetics of thermal dehydration of La(III) and Yb(III) complexes with ortho-vanillin oxime

The analysis of dehydration of the complexes, [La(C₈H₈NO₃)₃.2H₂O] and [Yb(C₈H₈NO₃)₃.3H₂O] for the evaluation of kinetic parameters (Z, E &S ^*) and mechanism of dehydration by non-isothermal methods are reported. The complexes decompose in three well defined steps involving random nucleation mechanism. First two steps involving the dehydration and the third step the loss of the ligand moiety. The intermediates formed during decomposition were found to be unstable for carrying out any significant studies.

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Zusammenfassung Zwecks Ermittlung der kinetischen Parameter (Z, E undS ^*) und des Mechanismus der Dehydratierung durch nichtisotherme Verfahren wird die Analyse der Dehydratierung der Komplexe [La(C₈H₈NO₃)₃·2H₂O] und [Yb(C₈H₈NO₃)₃·3H₂O] beschrieben. Die Komplexe zersetzen sich in drei gut definierten Schritten mit Random-Keimbildungsmechanismus. Die ersten zwei Schritte beinhalten die Dehydratierung, der dritte Schritt den Verlust der Liganden. Die wÄhrend der Zersetzung entstandenen Zwischenprodukte erwiesen sich für jegliche signifikante Untersuchung als zu unstabil.

     

Kinetics of thermal decomposition of iron(III) dicarboxylate complexes

Summary Tris(dicarboxylate) complexes of iron(III) with oxalate, maleate, malonate and phthalate viz. K₃[Fe(C₂O₄)₃]×3H₂O (1), K₃[Fe(OOCCH₂COO)₃]×3H₂O (2), K₃[Fe(OOCCH=CHCOO)₃]×3H₂O (3), K₃[Fe(OOC-1,2-(C₆H₄)-COO)₃]×3H₂O (4) have been synthesized and characterized using a combination of physicochemical techniques. The thermal decomposition behaviour of these complexes have been investigated under dynamic air atmosphere upto 800 K. All these complexes undergo a three-step dehydration/decomposition process for which the kinetic parameters have been calculated using Freeman-Carrol model as well as using different mechanistic models of the solid-state reactions. The trisoxalato and trismalonato ferrate(III) complexes undergo rapid dehydration at lower temperature below 470 K. At moderately higher temperatures (i.e. >600 and 500 K, respectively) they formed bis chelate iron(III) complexes. The trismalonato and trismaleato complexes dehydrate with almost equal ease but the latter is much less stable to decomposition and yields FeCO₃ below 760 K. The cis-dicarboxylate complexes particularly with maleate(2-) and phthalate(2-) ligands are highly prone to the loss of cyclic anhydrides at moderately raised temperatures. The thermal decomposition of the tris(dicarboxylato)iron(II) to iron oxide was not observed in the investigated temperature range up to 800 K. The dehydration processes generally followed the first or second order mechanism while the third decomposition steps followed either three-dimensional diffusion or contracting volume mechanism.     

Kinetics and mechanism of ligand substitution in binuclear nickel(II) and cobalt(II) complexes

The kinetics and mechanism of the removal of M²⁺ from bis-(heptane-2,4,6-trionato)M(II) [M = Ni, Co] by ethylenediminetetraacetic acid (EDTA), nitrilotriacetic acid (NAT), 1,2-cyclohexanediamine-N, N, N′, N′-tetraacetic acid (C_yDTA), and ethylenebis(oxyethylenenitrilo)tetraacetic acid (EGTA) have been investigated using stopped-flow spectrophotometry in methanol-water at 25°C and ionic strength 0.1 mol dm^?3 KNO₃. The reactions were investigated at a number of different pHs. An associative mechanism is proposed to account for the kinetic data. Although all the ligands have similar functional groups, their reactivity towards the parent complex is quite different. The pH dependence of the rate constants has been used to determine the relative reactivities of the various ligand species present. In the case of nitrilotriacetic acid, a nonlinear dependence on ligand concentration is observed, thus confirming the mechanism proposed. © 1995 John Wiley & Sons, Inc.     

Kinetics of oxidation-reduction destruction of trisdipyridylruthenium (III) in weakly alkaline and weakly acidic media

Conclusions The limiting and initiating stage in oxidation-reduction destruction of (Ru)Dipy ₃ ⁺ with the hydroxyl anion, and in acidic reaction with a water molecule.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1243–1247, June, 1988.     

Iron(III) and nickel(II) template complexes derived from benzophenone thiosemicarbazones

New iron(III) and nickel(II) chelates were synthesized by template reaction of 2,4-dihydroxy- and 2-hydroxy-4-methoxy-benzophenone S-methylthiosemicarbazones with 2-hydroxy- and 5-bromo-2-hydroxy-benzaldehydes. The template complexes were isolated as stable solids and characterized by elemental analysis, conductivity and magnetic measurements, IR, ¹H NMR, UV–Visible, and mass spectra. The crystal structure of N ¹-(2-hydroxy-4-methoxyphenyl)(phenyl)methylene-N ⁴-(2-hydroxy-phenyl)methylene-S-methyl-thiosemicarbazidato-Fe(III) was determined by X-ray diffraction. A five-coordinate, distorted square-pyramidal geometry was established crystallographically for the iron(III) complex. Cytotoxicity and proliferation properties were determined using human erythromyeloblastoid leukemia and HL-60 mouse promyelocytic leukemia cell lines. For K 562 and HL-60 cells, compounds 1a and 2b were found to be cytotoxic at concentrations of 10 and 20 µg mL^?1.     

Dimethylphosphinato and dimethylarsinato complexes of Sb(III) and Bi(III) and their chemistry

Abstract  

The reaction of Me₂PO₂H and Me₂AsO₂H with SbCl₃, BiCl₃, and Bi(NO₃)₃·5H₂O gave the complexes Sb(Me₂PO₂)₃, Sb(Me₂AsO₂)₃, (Me₂PO₂)₂Bi-Cl, Bi(Me₂AsO₂)₃, (Me₂PO₂)₂Bi(NO₃), and (Me₂AsO₂)₂Bi(NO₃)·H₂O, respectively. The arsinato complexes did not react with the Lewis bases pyridine, Ph₃P, and Ph₃As in acetone. The compounds Sb(Me₂AsO₂)₃ and (Me₂AsO₂)₂Bi(NO₃)·H₂O reacted to a small extent with nicotinic acid in methanol but Bi(Me₂AsO₂)₃ gave (Me₂AsO₂-BiO) _x in good yields. (Me₂AsO₂)₂Bi(NO₃)·H₂O in methanol quantitatively rearranged to new complexes with the same composition, [(Me₂AsO₂)₂Bi(NO₃)·H₂O]′ and [(Me₂AsO₂)₂Bi(NO₃)·H₂O]″ in the presence of pyridine. With thiophenol in air, Sb(Me₂AsO₂)₃ gave PhSSPh and Me₂As-SPh (1:1 mol ratio), (Me₂AsO₂-SbO) _x and some Sb(Me₂AsO₂)₃ was reformed, Bi(Me₂AsO₂)₃ gave (Me₂AsO₂-BiO) _x , PhSSPh, and Me₂As-SPh (1:0.6 mol ratio), whereas (Me₂AsO₂)₂Bi(NO₃)·H₂O quantitatively gave PhSSPh, thus acting as a catalyst for the air oxidation of thiophenol.     

Kinetics of the oxidation of iodide by copper(III)-imine-oxime complexes

Summary The copper(III)-imine-oxime complexes [Cu^III(Enio)]⁺ and [Cu^III(Pre)]⁺ {EnioH₂ =N,N-ethylene bis(isonitrosoacetylacetoneimine) and PreH₂ = N,N-propylene bis (isonitrosoacetylacetoneimine)} react very rapidly with iodide. The rate law under fixed conditions for the reaction is given by the equation: –d[Cu^III]/dt = (2k₂[I^–] + 2k₃[I^–]²)[Cu^III] The [Cu^III(Enio)]⁺ reaction was pH-independent whereas the [Cu (Pre)]⁺ reaction rate increased with increasing pH. Both the k₂ and the k₃ pathways are believed to involve one-electron transfer. An inner-sphere mechanism may operate in the pathway, first-order in [I^–].