Ruthenium(III) catalysis in the reaction of hexacyanoferrate(III) and iodide ions in perchloric acid medium

RuCl₃ can further catalyze the reaction between hexacyanoferrate(III) and iodide ions, which is already catalyzed by the hydrogen ions obtained from perchloric acid. Rate, when the reaction is catalyzed only by the hydrogen ions, was separated graphically from the rate when ruthenium(III) and H⁺ ions both catalyze the reaction. Reactions studied separately in the presence as well as in the absence of RuCl₃ under similar conditions were found to follow second order kinetics w.r.t. [I⁻]. While the rate showed direct proportionality w.r.t. [Fe(CN)₆]³⁻ and [RuCl₃]. At low concentrations the reaction shows direct proportionality with respect to [H⁺] which tends to become proportional to the square of hydrogen ion concentrations. External addition of [Fe(CN)₆]⁴⁻ ions retards the reaction velocity while change in ionic strength of the medium has no effect on the rate. With the help of the intercept of the catalyst graph, extent of the reaction, which takes place without adding ruthenium(III) was calculated and it was in accordance with the values obtained from the separately studied reaction in which only H⁺ ions catalyze the reaction. It is proposed that ruthenium forms a complex, which slowly disproportionates into the rate-determining step. Arrhenius parameters at four different temperatures were also calculated.      

Iridium(III) catalyzed oxidation of iodide ions in aqueous acidic medium

Oxidation of iodide ions by K₃Fe(CN)₆, catalyzed by hydrogen ions obtained from hydrochloric acid was found to be further catalyzed by iridium(III) chloride. Rate, when the reaction is catalyzed only by the hydrogen ions, was separated from the rate when iridium(III) and H⁺ions both, catalyze the reaction. Reactions studied separately in the presence as well as in the absence of IrCl₃ under similar conditions were found to follow second order kinetics with respect to [I⁻]. While the rate showed direct proportionality with respect to [K₃Fe(CN)₆] and [IrCl₃]. At low concentrations the reaction shows direct proportionality with respect to [H⁺] which tends to become proportional to the square of hydrogen ions at higher concentrations. Strong retarding affect of externally added hexacyanoferrate(II) ions was observed in the beginning but further addition affects the rate to a little extent. Changes in [Cl⁻] and also ionic strength of the medium have no effect on the rate. With the help of the intercept of catalyst graph, the extent of the reaction, which takes place without adding iridium(III), was calculated and was found to be in accordance with the values obtained from the separately studied reactions in which only H⁺ ions catalyze the reaction. It is proposed that iridium forms a complex, which slowly disproportionates into the rate-determining step. Thermodynamic parameters at four different temperatures were calculated.     

Co-catalysis by transition metal ions in the hydrogen ion catalysed oxidation of iodide ions. A kinetic study

The reaction between KI and [Fe(CN)₆]^3– ion, catalysed by hydrogen ions, was found to be catalysed further by PdCl₂. Separate reactions under similar conditions, studied in the absence as well as in the presence of PdCl₂ catalyst, were found to follow first order kinetics w.r. to [Fe(CN)₆]^3– and [H⁺], while the order was two w.r. to [I^–]. [Fe(CN)₆]^4– ions were found to have a negative effect while changes in ionic strength of the medium do not effect the reaction velocity. Reaction in the presence of PdCl₂ showed direct proportionality w.r. to [PdCl₂]. The rate and extent of the reaction, which takes place even at zero [PdCl₂] in the co-catalysed reaction, was calculated and was found to be in accordance with the rate values of the separately studied reaction at similar concentrations without adding PdCl₂.     

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     

Ruthenium (VIII) mediated oxidation of some aliphatic and alicyclic ketones by periodate-ruthenium (III) system in aqueous HClO4 medium

The kinetics of Ruthenium(III) chloride mediated oxidation of acetone, 2-butanone, 4-methyl-2-pentanone, 2-pentanone, cyclopentanone, and cyclohexanone by sodium periodate in aqueous HClO₄ media was zero-order in [IO₄⁻] and first-order in [ketone]. The reaction was independent of added [Ru(III)] and showed first-order dependence on [H⁺] for all the ketones studied, except acetone. In the case of acetone at [H⁺] < 0.05 M, the rate was independent of [H⁺], the order in [Ru(III)] being unity; but at [H⁺] > 0.05 M the reaction showed unit dependence on [H⁺] and the order in [Ru(III)] was zero. Ruthenium(VIII) generated in situ is postulated as the hydride abstracting species. A mechanism involving enolization as the rate determining step is proposed. Acetone at lower acidity of the medium is shown to react directly with Ru(VIII). In the absence of ruthenium(III) chloride, the kinetics were first-order in [IO₄⁻], [ketone], and [H⁺]. Structure-reactivity relationship is discussed and thermodynamic parameters are reported. © 1996 John Wiley & Sons, Inc.     

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.     

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     

The oxidation of thiosulphate ions by octacyanotungstate(V) in weak acidic medium

The kinetics of the oxidation of thiosulphate ions by octacyanotungstate(V) ions has been studied in the pH range 3.9–5.0. The reaction showed zero-order kinetics with respect to [W(CN)₈^3?] and is consistent with the rate law R = k[H⁺][S₂O₃^2?]². A reaction mechanism is proposed for the reaction with a third-order rate constant of 0.26 M^?2 s^?1 at 25°C.     

Kinetics and mechanism of the ligand substitution reaction between aquapentacyanoruthenate(II) and 4-cyanopyridine in the presence of anionic surfactant micelles

The kinetics of ligand substitution between aquapentacyanoruthenate(II) ion, [Ru(CN)₅H₂O]³⁻ and 4-cyanopyridine (4-CNpy) has been investigated spectrophotometrically in the presence of anionic surfactant micelle, namely sodium dodecylsulphate (SDS) at 400 nm (λ_max of the intense yellow product [Ru(CN)₅4-CNpy]³⁻) under pseudo-first-order conditions using at least 10% excess of 4-CNpy over [Ru(CN)₅H₂O]³⁻. The reaction was studied as a function of [Ru(CN)₅H₂O³⁻], [4-CNpy], [SDS], pH, ionic strength and temperature, by varying each of these variables one at a time. The reaction exhibited overall second-order kinetics, being first order each in [4-CNpy] and [Ru(CN)₅H₂O³⁻] over a wide concentration range. Variation of ionic strength of the medium had a significant negative effect on the rate. The SDS micelle, being negatively charged, does not reveal any regular effect except at or near its critical micelle concentration (c.m.c). The rate of reaction was measured at different temperatures, and the activation parameters were computed using Arrhenius and Eyring plots. A plausible mechanism consistent with the experimental results has been proposed.     

Mechanistic aspects of the reduction of ruthenium(III) catalyzed

The kinetics of Ru_III catalyzed reduction of hexacyanoferrate(III) [Fe(CN)₆]^3–, by atenolol in alkaline medium at constant ionic strength (0.80 mol dm^–3) has been studied spectrophotometrically, using a rapid kinetic accessory. The reaction between atenolol and [Fe(CN)₆]^3– in alkaline medium exhibits 1:2 stoichiometry [atenolol:Fe(CN)₆ ^3–]. The reaction showed first order kinetics in [Fe(CN)₆]^3– concentration and apparent less than unit order dependence, each in atenolol and alkali concentrations. Effect of added products, ionic strength and dielectric constant of the reaction medium have been investigated. A retarding effect was observed by one of the products i.e., hexacyanoferrate(II). The main products were identified by i.r., n.m.r., fluorimetric and mass spectral studies. A mechanism involving the formation of a complex between the atenolol and the hydroxylated species of ruthenium(III) has been proposed. The active species of oxidant and catalyst were [Fe(CN)₆]^3–and [Ru (H₂O)₅OH]²⁺, respectively. The reaction constants involved in the mechanism were evaluated. The activation parameters were computed with respect to the slow step of the mechanism, and discussed.     

Electron Transfer Reactions of Photochemically Generated Ruthenium(III)–Polypyridyl Complexes with Methionines

The oxidation of methionine (Met) plays an important role during biological conditions of oxidative stress as well as for protein stability. Ruthenium(III)–polypyridyl complexes, [Ru(NN)₃]³⁺, generated from the photochemical oxidation of the corresponding Ru(II) complexes with molecular oxygen, undergo a facile electron transfer reaction with Met to form methionine sulfoxide (MetO) as the final product. Interaction of [Ru(NN)₃]³⁺ with methionine leads to the formation of >S^+● and (>S∴S<)⁺ species as intermediates during the course of the reaction. The interesting spectral, kinetic, and mechanistic study of the electron transfer reaction of four substituted methionines with six [Ru(NN)₃]³⁺ ions carried out in aqueous CH₃CN (1:1, v/v) by a spectrophotometric technique shows that the reaction rate is susceptible to the nature of the ligand in [Ru(NN)₃]³⁺ and the structure of methionine. The rate constants calculated by the application of Marcus semiclassical theory to these redox reactions are in close agreement with the experimental values.     

The three‐dimensional coordination polymer tetra­ethyl­ammonium (ethyl­ene­di­amine)­cadmium(II) hexa­cyano­ferrate(III), (Et4N){[Cd(en)]4[Fe(CN)6]3}

The title compound, tetra­ethyl­ammonium dodeca‐μ‐cyano‐hexa­cyano­tetrakis­(ethyl­ene­di­amine)­tetra­cadmium(II)­tri­fer­rate(III), (C₈H₂₀N)[Cd₄Fe₃(CN)₁₈(C₂H₈N₂)₄], was pre­pared from a reaction mixture containing CdCl₂, K₃[Fe(CN)₆], ethyl­ene­di­amine (en) and [Et₄N]Br in a 1:1:3:1 molar ratio. The crystal structure consists of a negatively charged three‐dimensional framework of {[Cd(en)]₄[Fe(CN)₆]₃} anions, with [Et₄N]⁺ cations located in the cavities of the framework. The Cd atom is octahedrally coordinated by one disordered chelating en mol­ecule [mean Cd—N = 2.35 (3) Å] and four N‐­bonded bridging cyano groups [Cd—N distances are in the range 2.283 (2)–2.441 (2) Å]. There are two crystallographically independent [Fe(CN)₆]³⁻ anions in the structure and in each the Fe atom lies on a twofold axis. In the first [mean Fe—C = 1.941 (5) Å], all the cyano groups are bridging ligands, while in the second [mean Fe—C = 1.945 (2) Å], there are two terminal cyano ligands in trans positions. The Cd—N—C angles range from 128.6 (2) to 172.8 (2)°.     

The mechanism of a redox indicator reaction: The kinetics of oxidation of ferrocyphen by nitrous acid

Summary The oxidation of [Fe(phen)₂(CN)₂] and [Fe(bipy)₂(CN)₂] by nitrous acid in sulphuric acid follows the kinetic equation rate = k[H⁺] [HNO₂] [complex] at low acidities. The mechanism is a diffusion controlled reaction between NO⁺ and the complex. Reaction is too slow for satisfactory use as a redox indicator for nitrite titrations at low acidities (0.1 M) [H⁺]. The variation of rate with acidity in more concentrated sulphuric acid (up to 6 M) is interpreted in terms of protonation of the complex to form [Fe(phen)₂(CNH)₂]²⁺.We thank the British Council for a maintenance award for P.R., and the Universidad Tecnica Federico Santa Maria, Valparaiso, Chile, for study leave.     

Electrochemically induced transformations of ruthenium(III) trichloride microcrystals in salt solutions

Ruthenium (III) trichlorid solid crystals have been mechanically attached to gold surfaces and studied by cyclic electrochemical quartz crystal microbalance measurements in the presence of aqueous solutions of different concentrations containing M⁺Cl⁻, where M⁺=H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺. The RuCl₃ and the complexes formed during the electrochemical transformations show two or more reduction and reoxidation pairs of waves, depending on the experimental conditions (concentration, scan rate, and potential range). The voltammetric peaks are shifted into the direction of higher potentials with increasing electrolyte concentrations except at very high concentrations when the peaks belong to the first reduction/reoxidation processes move oppositely. The mass change was reversible, during reduction mass increase, while during oxidation mass decrease occurred at medium electrolyte concentrations in two, more or less distinct steps. At high or low concentrations the mass excursions are more complex involving different mass increase/decrease regions as a function of potential which vary with the potential range of the measurements. The peak potentials and the electrochemical activity strongly depend on the nature of the cations and pH. It is related to the formation of complexes in different compositions. The mass change decreases with increasing electrolyte concentrations attesting the important role of the water activity and the transport of solvent molecules. It was concluded that in dilute solutions during the first reduction step M⁺ ions enter the surface layer. The strongly hydrated Li⁺ ions transfer water molecules into the microcrystals, while simultaneously with the incorporation of K⁺, Rb⁺, and Cs⁺ ions H₂O molecules leave the surface layer. The opposite transport of ions and solvent molecules occur during oxidation. In the course of further reduction the incorporation of all ions studied except that of Cs⁺ ions is accompanied with water sorption. The number of sorbed water molecules is proportional to the hydration number of these ions. A reaction scheme is proposed in which M⁺ _m-3[Ru^IIICl _m (H₂O) _n ]^3-m · xH₂O (m≥3) and [Ru^IIICl _m (H₂O) _n ]^3-m (Cl⁻)_3-m · xH₂O (m≤3) type complexes are reduced to the respective – or depending on the electrolyte concentration higher or lower – Ru(II)chloro complexes resulting in mixed valence compounds (phases). Taking into account the layered structure of RuCl₃ the electrochemical reduction can be explained as an intercalation reaction in that mixed valence intercalation phases with a general formula M _x ⁺(H₂O) _y [RuCl₃] ^x− are formed from RuCl₃·x H₂O. The reduction/reoxidation waves are related to the redox transformations of Ru(III) to Ru(II) sites, while the composition of the polynuclear complexes and the structure of microcrystals change. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13.−16., 2005.     

Kinetics and mechanism of ligand exchange of coordinated cyanide in hexacyanoferrate(II) by nitroso‐R‐salt in the presence of mercury(II) as a catalyst

The kinetics of Hg(II)‐catalyzed reaction between hexacyanoferrate(II) and nitroso‐R‐salt has been followed spectrophotometrically by monitoring the increase in absorbance at 720 nm, the λ_max of green complex, [Fe(CN)₅ N‐R‐salt]^3? as a function of pH, ionic strength, temperature, concentration of reactants, and the catalyst. In this reaction, the coordinated cyanide ion in hexacyanoferrate(II) gets replaced by incoming N‐R‐salt under the following specified reaction conditions: temperature = 25 ± 0.1°C, pH = 6.5 ± 0.2, and I = 0.1 M (KNO₃). The stoichiometry of the complex has been established as 1:1 by mole ratio method. The rate of catalyzed reaction is slow at low pH values and then increases with pH and attains a maximum value between 6.5 and 6.7. The rate finally falls again at higher pH values due to nonavailability of [H⁺] ions needed to regenerate the catalytic species. The rate of reaction increases initially with [N‐R‐salt] and attains a maximum value and then levels off at higher [N‐R‐salt]. The rate of reaction shows a variable order dependence in [Fe(CN)₆^4?] ranging from unity at lower concentration to 0.1 at higher concentrations. The effect of [Hg²⁺] on the reaction rate shows a complex behavior and the same has been explained in detail. The activation parameters for the catalyzed reactions have been evaluated. A most plausible mechanistic scheme has been proposed based on the experimental observations. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 222–232, 2005     

The Preparation and Reactions of Cationic Ruthenium(II) Complexes Containing 1,5-Cyclooctadiene and Acetonitrile

The polymer [(C₈H₁₂)RuCl₂]x, (C₈H₁₂  1,5-cyclooctadiene, x > 2), dissolves in refluxing acetonitrile to form [(C₈H₁₂)RuCl(CH₃CN)₃]⁺ and, on treatment with AgPF₆, [(C₈H₁₂)Ru(CH₃CN)₄]²⁺; some reactions of these cations are described.     

Azido-, Rhodano-, Cyano- und Fluorokomplexe des Fe(III)-Ions in Dimethylsulfoxid

Zusammenfassung Auf Grund spektrophotometrischer und konduktometrischer Messungen wurden folgende Koordinationsformen des Eisen(III)-ions mit Azid-, Rhodanid-, Cyanid- und Fluoridionen in Dimethylsulfoxid festgestellt: [Fe(N₃)₄]^–, [Fe(SCN)₆]^3–, [Fe(CN)₂]⁺, Fe(CN)₃, [Fe(CN)₄]^–, [FeF₂]⁺, [FeF₄]^–.

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By means of spectrophotometric and conductometric measurements the following coordination forms of iron(III) with azide-, thiocyanate-, cyanide- and fluoride ions were found in dimethyl sulfoxide: [Fe(N₃)₄]^–, [Fe(SCN)₆]^3–, [Fe(CN)₂]⁺, Fe(CN)₃, [Fe(CN)₄]^–, [FeF₂]⁺, [FeF₄]^–.

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Mit 4 Abbildungen     

Thermal Activation of CH4 and H2 as Mediated by the Ruthenium Oxide Cluster Ions [RuOx]+ (x=1–3): On the Influence of Oxidation States

Thermal gas-phase reactions of the ruthenium-oxide clusters [RuO_x]⁺ (x=1–3) with methane and dihydrogen have been explored by using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. For methane activation, as compared to the previously studied [RuO]⁺/CH₄ couple, the higher oxidized Ru systems give rise to completely different product distributions. [RuO₂]⁺ brings about the generations of [Ru,O,C,H₂]⁺/H₂O, [Ru,O,C]⁺/H₂/H₂O, and [Ru,O,H₂]⁺/CH₂O, whereas [RuO₃]⁺ exhibits a higher selectivity and efficiency in producing formaldehyde and syngas (CO+H₂). Regarding the reactions with H₂, as compared to CH₄, both [RuO]⁺ and [RuO₂]⁺ react similarly inefficiently with oxygen-atom transfer being the main reaction channel; in contrast, [RuO₃]⁺ is inert toward dihydrogen. Theoretical analysis reveals that the reduction of the metal center drives the overall oxidation of methane, whereas the back-bonding orbital interactions between the cluster ions and dihydrogen control the H−H bond activation. Furthermore, the reactivity patterns of [RuO_x]⁺ (x=1–3) with CH₄ and H₂ have been compared with the previously reported results of Group 8 analogues [OsO_x]⁺/CH₄/H₂ (x=1–3) and the [FeO]⁺/H₂ system. The electronic origins for their distinctly different reaction behaviors have been addressed.     

Kinetic and mechanism of pentacyanohydroxoferrate(III) formation from the reaction of [Fe2HPDTA(OH)2] with cyanide ions

Summary The kinetics and mechanism of exchange of HPDTA in [Fe₂HPDTA(OH)₂] with cyanide ion (HPDTA=2-hydroxytrimethylenediaminetetraacetic acid) was investigated spectrophotometrically by monitoring the peak at 395 nm ( _max of [Fe(CN)₅OH]^3– at pH=11.0±0.02,I=0.25m (NaClO₄) at ±0.1°C).Three distinct observable stages were identified; the first is the formation of [Fe(CN)₅OH]^3–, the second the formation of [Fe(CN)₆]^3– from it and the third the reduction of [Fe(CN)₆]^3– to [Fe(CN)₆]^4– by HPDTA^4– released in the first stage.The first stage follows first-order kinetics in [Fe₂HPDTA(OH)₂] and second-order in [CN^–] over a wide range of [CN^–], but becomes zero order at [CN^–]<5×10^–2 m. We suggest a cyanide-independent dissociation of [Fe₂HPDTA)(OH)₂] into [FeHPDTA(OH)] and [Fe(OH)]²⁺ at low cyanide concentrations and a cyanide-assisted rapid dissociation of [Fe₂HPDTA(OH)₂] to [FeHPDTA(OH)(CN)]^3– and [Fe(OH)]²⁺ at higher cyanide concentrations. The excess of cyanide reacts further with [FeHPDTA(OH)(CN)]^3– finally to form [Fe(CN)₅OH]^3–.The reverse reaction between [Fe(CN)₅OH]^3– and HPDTA^4– is first-order in [Fe(CN)₅OH]^3– and HPDTA^4–, and exhibits inverse first-order dependence on cyanide concentration.A six-step mechanism is proposed for the first stage of reaction, with the fifth step as rate determining.     

Improved synthesis and crystal structure of tetrakis(acetonitrile)(η-1,5-cyclooctadiene)ruthenium(II) bis[tetrafluoroborate(1−)]

An improved, one-step synthesis of [Ru^II(1,5-COD)(CH₃CN)₄]²⁺ as the BF₄⁻ salt has been accomplished in 51% yield, an approximately 75% higher yield than the three-step literature synthesis of the corresponding PF₆⁻ salt. The improved synthesis consists of (i) grinding the insoluble [RuCl₂(1,5-COD)]_x precursor to increase the reaction rate and yield, (ii) treating the resultant [RuCl₂(1,5-COD)]_x with 2Ag⁺BF₄⁻ in refluxing acetonitrile with excess 1,5-COD present to inhibit 1,5-COD loss in the product and, most importantly, (iii) following the reaction directly by ¹H-NMR spectrometry which revealed that the substitution reaction of the Ru(II), d⁶ precursor is, as expected, quite slow and requires ca. 120 h. The [Ru(1,5-COD)(CH₃CN)₄][BF₄]₂ product was characterized by ¹H, ¹³C, and ¹⁹F-NMR, elemental analysis, and single-crystal X-ray crystallography. Problems in commercial Ru and F analyses are also addressed since this issue has been inadequately treated in the existing literature.