Kinetics and mechanism of the oxidation of glycolaldehyde by tetrachloroaurate(III)

The kinetics of the reaction between glycolaldehyde (GA) and tetrachloroaurate(III) in acetic acid-sodium acetate buffer has been studied. The reaction is first-order with respect to [Au^III] as well as [GA]. Both H⁺ and Cl⁻ ions retard the rate of reaction. AuCl₄⁻, AuCl₃(OH₂), and AuCl₃(OH)⁻ are the reactive species of gold(III) with gradually increasing reactivity. A reaction mechanism involving two-electron transfer rate determining steps has been proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 613–619, 1998     

Kinetics and mechanism of oxidations by metal ions. Part 16. Oxidation of 4-oxopentanoic acid by aquomanganese(III) ions

Summary The outer-sphere oxidation of 4-oxopentanoic acid (4-OPA) to MeCO₂H by aquomanganese(III) ions exhibits a first-order dependence on [4-OPA] and [Mn(III)](aq). The observed pseudo first-order rate constant k _obs ([4-OPA] [Mn^III](aq)) is independent of [Mn^II] but decreases with increasing [H⁺]. The retarding effect of [H⁺] on the observed rate could be explained by considering either the reaction between MnOH⁺(aq) and MeCOCH₂— CH₂CO₂H or between Mn³⁺(aq) and MeCOCH₂CH₂-COO^– ions. The rate constant for the latter pair of reactants is much higher than the rate constant for the reaction between the first pair. Since the activation enthalpy for the first pair is about 14 kJ mol^–1 less than that of the second pair, it is concluded that the reactive species are MnOH²⁺(aq) and MeCOCH₂CH₂CO₂H or that the preferred oxidant is MnOH²⁺(aq) ion.     

Kinetics and mechanism of the oxidation of chromium(III)–dipicolinic acid complex by N-bromosuccinimide

The kinetics of oxidation of the chromium(III)–dipicolinic acid complex [Cr^III(DPA)₂(H₂O)₂]^– by N-bromosuccinimide (NBS) in aqueous solution to Cr^VI have been studied spectrophotometrically over the 20–40 °C range. The reaction is first order with respect to both [NBS] and [Cr^III], and increases with pH over the 5.92–6.93 range. Thermodynamic activation parameters were calculated. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of [NBS] to chromium(III).     

The Tetrachloridoaurates(III) of Zinc(II) and Cadmium(II)

The first salt‐like compounds of dications with [AuCl₄]^– anions are reported. The compounds Zn[AuCl₄]₂ · (AuCl₃)_1.115 ( 1 ) and Cd[AuCl₄]₂ ( 2 ) are obtained from reactions of MCl₂ (M = Zn, Cd) and elemental gold in liquid chlorine at ambient temperature under autogenous pressure and subsequent annealing at 230 °C. The structure of 1 represents an incommensurately modulated composite [superspace group C2/c(α0γ)0s] built of two subsystems. The first subsystem contains chains of zinc(II) tetrachloridoaurate(III), which feature a slightly distorted octahedral coordination of Zn and can be described by the Niggli formula ¹_∞{Zn[AuCl₄]_1/1[AuCl₄]_2/2}. The second subsystem consists of Au₂Cl₆ molecules, which are located in channels built up by the first subsystem. The structural parameters of the hosted Au₂Cl₆ molecules show only small deviations from neat AuCl₃. The crystal structure of Cd[AuCl₄]₂ ( 2 ) consists of chains built of Cd²⁺ ions coordinated by bridging [AuCl₄]^– anions and alternating Cd‐Au sequence. Cd has a distorted octahedral coordination environment.     

Kinetik und Mechanismus der Substitutionsreaktionen von Komplexverbindungen, 22. Mitt.: Neue Derivate der Bis-dimethylglyoximato-diselenocyanato-kobalt(III)-säure und die Kinetik der Aquotisierung des Komplexes

Zusammenfassung Es wurden 29 neue Komplexsalze der Säure: H[CoDim ₂ ^**(NCSe)₂] erhalten. Spektrophotometrische Messungen wurden im UV- und IR-Bereiche durchgeführt. Die Kinetik der Aquotisierung der [CoDim ₂(NCSe)₂]^–-Ionen wurde untersucht. Die Ergebnisse wurden mit den kinetischen Parametern der Aquotisierung der analogen [Co_{Dim 2} X ₂]^–-Ionen (mitX=Cl, Br, J, NCS) verglichen.

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Kinetics and mechanism of substitution reactions in complex compounds, XXII.: New derivatives of hydrogen bis-(dimethyl-glyoximatodiselenocyanato)-cobaltiatic(III) acid and kinetics of the hydrolysis of the [CoDim₂(NCSE)₂]^– ion

A series of 29 novel complex salts of the acid H[CoDim ₂(NCSe)₂] has been prepared and characterized. UV, Vis. and IR spectra were recorded and the aquation kinetics of the [CoDim ₂(NCSe)₂]^– ions studied. Results were compared with kinetic parameters of the aquation of the analogous [CoDim ₂ X ₂]^– ions, whereX=Cl, Br, J, SCN.

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Aquotisierung = Austausch eines Komplexliganden gegen Wasser.     

Chelate polypyridine ligand rearrangement in Au(III) complexes

The reaction of gold(III) neutral complexes AuBr(CN)₂(N–N) {N–N = 2,2′-bipyridine (bpy), 5,5′-dimethyl-2,2′-bipyridine (^Me2bpy), 1,10-phenanthroline (phen)} with a stoichiometric amount of K[AuCl₄] · 2H₂O in nitromethane at room temperature led to the formation of 1:1 electrolytes which were characterized by NMR and IR spectroscopy, conductivity measurements, elemental analyses and X-ray diffraction. Both the anions and the cations of these salts are singly charged square-planar Au(III) complexes and the cations have general formula [AuCl₂(N–N)]⁺. A hypothesis on the possible reaction mechanisms is presented to give an explanation for the formation of the reaction products.     

Triethylenetetraminehexaacetatoferrato(II)cuprate(II), [FeIICuII-(ttha)]2−: oxidation-induced cross-binuclear metal exchange

Summary The heterobinuclear complex [Fe^IICu^II(ttha)]^2– (1) (ttha^6– = triethylenetetraminehexaacetate), exhibits the same two-nitrogen per metal coordination of the related homobinuclear [Cu _inf2 ^supII (ttha)]^2– complex, but(1) has a signature broad single derivative e.p.r. line atg = 2.11 with a peak-to-peak width of 182 G. Oxidation to the [Fe^IIICu^II(ttha)]^– complex by either O₂ or H₂O₂ initiates a rapid cross-binuclear metal exchange forming homobinuclear [Fe _inf2 ^supIII O(ttha)]^2– and [Cu _inf2 ^sup– (ttha)]^2– products (t _1/2 ca 3.9 s). An isomeric form of [Fe^IIICu^II(ttha)]^–, which has three nitrogen donors bound to Cu^II and only the remaining iminodiacetate fragment bound to Fe^III, rearranges much more slowly (t _1/2 ca 4.8 h).     

Syntheses,crystal structures and magnetic properties of two cyano-bridged two-dimensional assemblies [Fe(salpn)]2 [Fe(CN)5NO] and [Fe(salpn)]2[Ni(CN)4]

Two cyano-bridged assemblies, [Fe^III(salpn)]₂[Fe^II(CN)₅NO] (1) and [Fe^III (salpn)]₂[Ni^II(CN)₄] (2) [salpn = N, N-1,2-propylenebis(salicylideneiminato)dianion], have been prepared and structurally and magnetically characterized. In each complex, [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– coordinates with four [Fe(salpn)]⁺ cations using four co-planar CN^– ligands, whereas each [Fe(salpn)]⁺ links two [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– ions in the trans form, which results in a two-dimensional (2D) network consisting of pillow-like octanuclear [—M^II—CN—Fe^III—NC—]₄ units (M = Fe or Ni). In complex (1), the NO group of [Fe(CN)₅NO]^2– remains monodentate and the bond angle of Fe^II—N—O is 180.0°. The variable temperature magnetic susceptibilities, measured in the 5–300 K range, show weak intralayer antiferromagnetic interactions in both complexes with the intramolecular iron(III)iron(III) exchange integrals of –0.017 cm^–1 for (1) and –0.020 cm^–1 for (2), respectively.     

Aqueous polymerization of acrylonitrile initiated by manganese(III) pyrophosphate-thiocyanate redox system: a kinetic study

Summary The kinetics of aqueous polymerization of acrylonitrile monomer (M) initiated by the Mn^III-KNCS redox system have been studied under deaerated conditions in the temperature range 26–40 °C at constant ionic strength. The overall rates of polymerization and the disappearance of Mn^III were determined. The polymerization was initiated by the free radicals arising from the Mn^III-thiocyanate redox reaction. The rate of polymerization was investigated at various concentrations of monomer and initiator. The effects of varying [Mn^III], [NCS^–], pH, total [P₂O _inf7 ^sup4– ], added [Mn^II], metal ions, ClO _inf4 ^sup– , Cl^– and SO _inf4 ^sup2– were examined. Dependence of the rate of polymerization on temperature was studied and activation parameters were computed from an Arrhenius plot. A suitable kinetic scheme consistent with the observed results is proposed and discussed.     

Structure of Tetranuclear Iron(III) d- and dl-Tartrates in Aqueous Solutions

The geometric parameters of dl- and d-tetranuclear iron(III) tartrates [Fe₄(d-L)₂(l-L)₂(H₂O)₈]^4–and [Fe₄(d-L)₄(H₂O)₈]^4–(H₄L is tartaric acid) were optimized using the molecular mechanics method (MIND program, Dashevskii–Plyamovatyi model).     

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^–].     

Kobalt(III) ammin-derivate einiger Reineckesalz-Analoga mit Toluidinen

Zusammenfassung Es wurden 39 neue Komplexsalze durch doppelte Umsetzung aus wäßrig-alkohol. Lösungen der folgenden Reineckeat-Analoga: [Cr(NCS)₄(o-Toluidin)₂]^–, [Cr(NCS)₄(m-Toluidin)₂]^– und [Cr(NCS)₄(p-Toluidin)₂]^– und Hexammin-, Monoacido-pentammin-und Diacido-tetrammin-kobalt(III)-komplexsalze erhalten.Es wurden in einigen Fällen Abweichungen in physikochemischen Eigenschaften, wie Farbtönung, Kristallform, Löslichkeit und papierchromatographischeR _F-Werte, bei den stellungsisomeren Salzen vom Typus: Kation·[Cr(NCS)₄(Toluidin)₂] und auch bei den Koordinationsisomerpaaren: [Co(DH)₂(o-Toluidin)₂][Cr(NCS)₄(p-Toluidin)₂] und [Co(DH)₂(p-Toluidin)₂] [Cr(NCS)₄(o-Toluidin)₂], usw. beobachtet.

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Cobalt(III) ammine derivatives of some reineckate analogues with toluidines

39 new complex salts were prepared by double conversion of the reineckate analogues [Cr(SCN)₄(o-toluidine)₂]^–, [Cr(SCN)₄(m-toluidine)₂]^–, and [Cr(SCN)₄(p-toluidine)₂]^– with the hexammine, monoacido-pentammine and diacido-tetrammine complexes of Co(III). In some of the position and coordination isomers deviations from the standard physico-chemical properties, i.e. color, crystal form, solubility and paper chromatographyR _f-values were observed.

     

Plasma desorption mass spectrometry of transition metal complexes of thio- and selenosemicarbazones of 2-acetylpyridines

Summary Californium-252 plasma desorption mass spectra were recorded for complexes of the anions of various thio-and seleno-semicarbazones of 3-acetylpyridines(1–4) with the transition metal ions iron(III) and cobalt(II). Positive ion spectra gave clear evidence of the cation present and fragmentation with loss of ligands or parts of ligands was straightforward. Negative ion spectra likewise provided evidence of the intact anion except with tetracoordinate metal halide systems [MX₄]^– which lost one or more halide atoms. Evidence of fragmentation of the ligand and recombination of the fragments with the metal ion was also observed in the negative ion mode. Spectra were used to revise the structure of a complex previously reported as [FeLCl₂]⁽¹⁾ to [FeL₂]⁺[FeCl₄]^–.     

Formation of the heteropolynuclear complex ([NH2(C4H9)2][Au{S2CN(C4H9)2}2][CdCl4])n during the chemisorption of gold(III) with cadmium dibutyldithiocarbamate: Structure and thermal properties

The chemisorption properties of cadmium dibutyldithiocarbamate with respect to [AuCl₄]⁻ in 2M HCl solutions are studied. The heterogeneous reaction of gold(III) binding affords the heteropolynuclear compound ([NH{₂(C₄H₉)₂][Au{S₂CN(C₄H₉)₂}₂][CdCl₄]) _n (I). The molecular and crystal structures of compound I are determined from the X-ray diffraction data. Each of three ions is presented in the structure by two conformers. The irreversible decomposition of some dibutyldithiocarbamate groups is observed during the chemisorption of gold(III), which noticeably decreases the efficiency of gold binding with the sorbent studied and its sorption capacity. The study of the thermal properties of compound I shows that gold(III) is reduced to the metal during thermolysis.     

Hexamethylphosphorsäuretriamid als Ligand, 3. Mitt.: Umsetzungen von [Co(HMPT)4]2+ mit Rhodanid-, Cyanid- und Azidionen

Zusammenfassung Auf Grund spektrophotometrischer, potentiometrischer und konduktometrischer Befunde entstehen aus [Co(HMPT)₄]²⁺ in Hexamethylphosphorsäuretriamid (HMPT) bei Zusatz von Pseudohalogenidionen folgende Koordinationsformen: [Co(HMPT)₃N₃]⁺, [Co(HMPT)₂(N₃)₂], [Co(HMPT)(N₃)₃]^–, [Co(N₃)₄]^2–, [Co(HMPT)₃NCS]⁺, [Co(HMPT)₂(NCS)₂], [Co(HMPT)(NCS)₃]^–, [Co(NCS)₄]^2–, [Co(HMPT)₂(CN)₂], [Co(HMPT)(CN)₃]^–, [Co(HMPT)(CN)₅]^3–.

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Hexamethyl phosphoric triamide as a ligand, III: Reactions of [Co(HMPT)₄]²⁺ with rhodanide, cyanide, and azide ions, resp

Spectrophotometric, potentiometric and conductometric results indicate that addition of pseudohalide ions to [Co(HMPT)₄]²⁺ in hexamethylphosphoramide (HMPT) leads to the following coordination forms: [Co(HMPT)₃N₃]⁺, [Co(HMPT)₂(N₃)₂], [Co(HMPT)(N₃)₃]^–, [Co(N₃)₄]^2–, [Co(HMPT)₃NCS]⁺, [Co(HMPT)₂(NCS)₂], [Co(HMPT)(NCS)₃]^–, [Co(NCS)₄]^2–, [Co(HMPT)₂(CN)₂], [Co(HMPT)(CN)₃]^–, [Co(HMPT)(CN)₅]^3–.

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2. Mitt.:V. Gutmann undA. Weisz, Mh. Chem.100, 2104 (1969).     

Kinetics and mechanism of oxidation of some reducing sugars by diperiodatoargentate(III) in alkaline medium

Summary The kinetics of oxidation of d-glucose, d-galactose, d-fructose, d-ribose, d-arabinose, d-xylose and 2-deoxyd-glucose by diperiodatoargentate(III) (DPA) have been investigated in alkaline medium. The order of the reaction with respect to [DPA] is unity while the order with respect to [sugar] is < 1 over the concentration range studied. The rate increases with an increase in [OH ^–] and there is a marginal decrease in the rate with an increase in [IO _inf4 ^sup– ]. No significant dependence on ionic strength was found, but the rate increases with a decreasing dielectric constant. Formic acid and the corresponding aldonic acids were detected as the products of oxidation. The participation of the open chain form of the sugar and a mechanism involving the initial formation of a complex between the enediol of the sugar and Ag^III are proposed.     

Understanding the microcrystal tests of three related phenethylamines: the ortho‐metallated (±)‐amphetamine formed with gold(III) chloride,and the tetrachloridoaurate(III) salts of (+)‐methamphetamine and (±)‐ephedrine

The ortho‐metallation product of the reaction of (±)‐amphetamine with gold(III) chloride, [D,L‐2‐(2‐aminopropyl)phenyl‐κ²N,C¹]dichloridogold(III), [Au(C₉H₁₂N)Cl₂], and the two salts resulting from crystallization of (+)‐methamphetamine with gold(III) chloride, D‐methyl(1‐phenylpropan‐2‐yl)azanium tetrachloridoaurate(III), (C₁₀H₁₆N)[AuCl₄], and of (±)‐ephedrine with gold(III) chloride, D,L‐(1‐hydroxy‐1‐phenylpropan‐2‐yl)(methyl)azanium tetrachloridoaurate(III), (C₁₀H₁₆NO)[AuCl₄], have different structures. The first makes a bidentate complex directly with a dichloridogold(III) group, forming a six‐membered ring structure; the second and third each form a salt with [AuCl₄]⁻ (each has two formula units in the asymmetric unit). The organic components are all members of the same class of stimulants that are prevalent in illicit drug use. These structures are important contributions to the understanding of the microcrystal tests for these drugs that have been employed for well over 100 years.     

Kinetics of ammoniation of some halobis(ethylenediamine)-rhodium(III) perchlorates in liquid ammonia

Summary The ammoniation ofcis-[Rh(en)₂Cl₂] · (ClO₄) in liquid NH₃ was studied at constant ionic medium of 0.20 m perchlorate in the 0 to 35° range. The complex reacts in two distinct steps to givecis-[Rh(en)₂(NH₃)₂] · (ClO₄)₃, with the intermediate formation ofcis-[Rh(en)₂(NH₃)Cl] · (ClO₄)₂. Both steps follow a conjugate-base mechanism. Activation parameters were obtained for the acid-base preequilibrium and the rate-determining step. The entropies of activation for the rate-determining step are 0 and –42 JK^–1mol^–1 for the first and second ammoniations respectively. These values are considerably lower than those found for the cobalt(III) analogues. The entropy changes for the acid-base equilibria are –84 and –36 JK^–1mol^–1 respectively, which is less negative than those values found for the cobalt(III) analogues. Trans-[Rh(en)₂I₂] · (ClO₄) ammoniates totrans-[Rh(en)₂(NH₃)I] · (ClO₄)₂. The contribution of spontaneous ammoniation to the overall reaction oftrans-[Rh(en)₂I₂] · (ClO₄) is negligible, so the uniqueness oftrans-[Co(en)₂Cl₂] · (ClO₄) among cobalt(III) complexes in this respect is not reproduced for thetrans-dihalotetraamine structure in rhodium(III) complexes. A comparison of cobalt(III) and rhodium(III) amines with respect to activation parameters and the influence of formal charge of the metal complex on reactivity indicates a more associative type of activation for rhodium(III).     

Kinetics and mechanism of the reduction of gold(III) by glycine in acetate buffer

The kinetics of reduction of tetrachloroaurate(III) by glycine has been spectrophotometrically studied in NaOAc–AcOH buffer in the pH range 3.73–4.77. The reaction is first order with respect to both Au(III) and glycine. Both H⁺ and Cl⁻ ions have inhibiting effects on the reaction rate. The rate decreases with a decrease in the dielectric constant of the medium. AuCl₄⁻ and AuCl₃(OH)⁻ are presumed to be the predominant oxidizing species under the conditions of the experiment. The reaction of gold(III) and zwitterionic species of glycine proceeds with the intermediate formation of gold(I) and iminic cation and the latter subsequently hydrolyses in a fast step to produce formaldehyde and ammonium ion. Formaldehyde was identified as the only organic product by ¹H NMR spectroscopy.     

Kinetics and mechanisms of oxidations by metal ions. Part 17. Oxidation of formate ion by alkaline osmium tetroxide

Summary The oxidation of formate ion by alkaline osmium tetroxide, such that [HCO _inf2 ^p– ] [Os^VII], exhibits first-order dependence in [Os^VII], an order less than unity in [HCO _inf2 ^p– ], and zero-order in [OH^–]. HCO^2– reacts as an ion-pair formed with an alkali metal ion and [OsO₄(OH)₂]^2– is the reactive species of Os^VII. The formation of an intermediate Os^VII-HCO₂M complex is substantiated by the rapid-scan spectra of the reaction mixture. Anions (Cl^–, ClO _inf4 ^p– ) have no effect on the rate. The close agreement between the observed k _H/k _D = 7.1 and the theoretically calculated value (7.0), based on the stretching frequencies of C-H and C-D bonds in the free molecule, indicates an outer-sphere mechanism.Author to whom all correspondence should be directed.