Kinetics and Mechanism of Oxidation of Azide Ion by 12-Tungstocobaltate(III), [CoW12O40]5-, Ion

Goyal, Bharti; Mehrotra, Manu; Prakash, Aditya; Mehrotra, Raj N.

doi:10.1515/irm-2000-0406

Cited by 7 publications

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“…However, the k obs is independent of the ionic strength, Table 4, indicating that the reaction partners are either molecular species or an ion and a molecular species. The present reaction in this respect is different from the similar oxidation with 12-tungstocobalt (III) ion [11]. …”

Section: Resultscontrasting

confidence: 78%

“…Depending on the nature of the oxidant, both inner and outer-sphere mechanisms have been observed. The oxidations by one-electron oxidants such as Co 3+ (aq) [5], Mn 3+ (aq) [6], [Mn(bipy) 2 OH] 2+ [7], [Mn(edta)(H 2 O] - [8], Ce 4+ (aqV) [9], [Ni(bipy) 3 ] 3+ [10] and [Co(III)O 4 W 12 O 36 ] 5-(abbreviated to [Co(III)W] 5-) [11] in acidic medium, and by two-electron oxidants viz. [Ag(OH) 4 ] - [12], [Cu III (H 2 TeO 6 ) 2 ] 5-and [Ag III (H 2 TeO 6 ) 2 ] 5- [13] in alkaline medium and [(CH 2 ) 2 (C 2 N 5 H 6 ) 2 Ag] 3+ , ethylenebisbiguanidesilver(III) in acidic medium [14] are inner-sphere.…”

Section: Introductionmentioning

confidence: 99%

“…The rates reported for the corresponding reaction with IrCl 6 3-in[11] were measured at the Centre for Fast Kinetics Research at the University of Texas at Austin.…”

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confidence: 99%

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Mechanism of the oxidation of hydrazoic acid by tetrachloroaurate(III) ion

Soni

Mehrotra

2008

Transition Met Chem

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The oxidation of hydrazoic acid in perchloric acid in the absence of added chloride under pseudo first-order conditions ([HN 3 ] » [AuCl 4 -]) is first order in [Au(III)]. Michaelis-Menten type of dependence (linear plots of k obs -1 vs [HN 3 ] -1 ) is observed with respect to [HN 3 ]. The k obs is independent of ionic strength and the plot between k obs -1 and [H + ] is linear. The inner-sphere mechanism is consistent with the formation of an axial complex (K = 25 dm 3 mol -1 ) between AuCl 3 (HO) -ion and HN 3 prior to its rate determining decomposition (k = 0.0182 s -1 ). It is inferred that the free radicals N 3• do not oxidise Au(II). The reaction becomes outer-sphere in the presence of added Cl -ions which are inferred to form a cage around the hydronium ion surrounding the AuCl 4 -ions. The penetration of N 3 -through the cage is rate controlling and within the cage, the electron transfer from N 3 -ion to AuCl 4 -is fast. The value of the rate determining constant k 2 is 0.547 dm 3 mol -1 s -1 and the equilibrium constant K Cl for the cage formation is 5 dm 3 mol -1 at 25°C. It is calculated that the minimum HN 3 concentration required before the reaction exhibits zeroorder dependence in HN 3 is 0.31 mol dm -3 when [H + ] = 0.18 mol dm -3 at 25°C.

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Section: Resultscontrasting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Mechanism of the oxidation of hydrazoic acid by tetrachloroaurate(III) ion

Soni

Mehrotra

2008

Transition Met Chem

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“…Sb(III) solution was prepared by dissolving SbCl 3 (British Drug House (BDH)) in 3.5 mol dm −3 HCl and standardized against bromate in 3.5 mol dm −3 HCl. The cobalt complexes [Co III W 12 O 40 ] 5− and [Co II W 12 O 40 ] 6− were prepared by the reported method 30, 31 and standardized spectrophotometrically 32 (at 624 nm, ε 624 = 180 ± 2 dm 3 mol −1 cm −1 for [Co II W 12 O 40 ] 6− and at 388 nm, ε 388 = 1150 ± 2 dm 3 mol −1 cm −1 for [Co III W 12 O 40 ] 5− , respectively) using an Elico SL 159 UV–vis spectrophotometer. The solution of Sb(V) was prepared by dissolving K[Sb(OH) 6 ] in 2 mol dm −3 HCl and its concentration was ascertained by iodometric titration with standard thiosulphate.…”

Section: Methodsmentioning

confidence: 99%

Kinetics and mechanism of oxidation of antimony(III) by keggin‐type 12‐tungstocobaltate(III) in aqueous hydrochloric acid medium

Bhosale

Gokavi

2002

Int J of Chemical Kinetics

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The reaction between Sb(III) and [Co III W 12 O 40 ] 5− proceeds with two, one-electron steps; formation of unstable Sb(IV) is the slow first step followed by its reaction with another oxidant in a fast step. The reaction rate is unaffected by the [H + ] as there are no protonation equlibria involved with both the reactants, whereas the accelerating effect of chloride ion is due to the formation of an active chlorocomplex of the reductant, SbCl 6 3− . Increase in the ionic strength and decrease in the relative permittivity of the medium increases the rate of the reaction, which is attributed to the formation of an outer-sphere complex between the reactants. The activation parameters were also determined and these values support the proposed mechanism.

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“…The results obtained indicates that the reaction proceeds with an outer-sphere electron transfer between the oxidant and the catalyst producing Ru(IV) in the first step as the 12-tungstocobaltate(III) ion is substitution inert [27,30]. In the next fast step arsenic(III) is oxidised by ruthenium(IV) regenerating the catalyst, with the formation of arsenic(IV).…”

Section: Discussionmentioning

confidence: 99%

Oxidation of Arsenous Acid by 12-Tungstocobaltate(III) Catalysed by Ruthenium(III) in Aqueous Acid Medium

Bhosale¹,

Gokavi²

2004

BioInorganic Reaction Mechanisms

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Ruthenium(III)-catalysed arsenic(III) oxidation by 12-tungstocobaltate(III) was found to proceed with transfer of an electron from catalyst to oxidant generating an intermediate ruthenium(IV). In the next step ruthenium(IV) abstract an electron from arsenic(III) leading to form arsenic(IV), which further reacts with oxidant to give arsenic(V). The active catalyst species was RuCl 5 (H 2 O) 2and due to formation of the inactive higher chloro-complex, RuCl 6 3-, inhibition of the reaction occurs as chloride ion concentration increases. There was no effect of hydrogen ion concentration on the reaction due to absence of any protonation equilibria under experimental conditions. The reaction was also catalysed by alkali metal cations due to ion pair formation between 12-tungstocobaltate(III) and alkali metal cations.

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Kinetics and Mechanism of Oxidation of Azide Ion by 12-Tungstocobaltate(III), [CoW12O40]5-, Ion

Cited by 7 publications

References 0 publications

Mechanism of the oxidation of hydrazoic acid by tetrachloroaurate(III) ion

Mechanism of the oxidation of hydrazoic acid by tetrachloroaurate(III) ion

Kinetics and mechanism of oxidation of antimony(III) by keggin‐type 12‐tungstocobaltate(III) in aqueous hydrochloric acid medium

Oxidation of Arsenous Acid by 12-Tungstocobaltate(III) Catalysed by Ruthenium(III) in Aqueous Acid Medium

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