Outer-sphere Pathway Research Articles

Mechanistic study on C(sp2)–F bond activation by a Ni0(silyl)-ate complex: an outer-sphere pathway via Ni0-mediated nucleophilic aromatic substitution

DFT calculations and AIMD simulations reveal C(sp2)–F bond activation by a Ni0(silyl)-ate complex, involving an outer-sphere pathway via Ni0-mediated SNAr.

Highly efficient electrosynthesis of hydrogen peroxide through the combination of side aeration and vacuum filtration modified graphite felt

The electrocatalytic activity towards two electron oxygen reduction reaction of graphite felt was advanced by incorporating carbon nitride, carbon nanotubes and polytetrafluoroethylene through vacuum filtration, which prevented the cleavage of O-O bond, facilitated the charge transfer, and established more three-phase active sites. To ameliorate the oxygen transfer process, the configuration of side-aeration was proposed, providing forced convection to reduce the thickness of diffusion layer, and increasing the dissolved oxygen. By simplified combination of refining the orientation of gas flow and modified graphite felt, the dual-chamber configuration rendered a qualitative leap in H2O2 generation capacity to 4.44–6.89 mg h−1 cm−2. The alkaline affinity of developed system was discussed in terms of a beneficial outer-sphere electron transfer pathway, the variation on adsorption strength of oxygenated species and working electrode potential range. Finally, Long-term operation stability and successful application in Electro-Fenton indicated great potential of developed system for H2O2 synthesis and environmental remediation.

Electron Transfer Reaction of Theobromine and Permanganate Ion in Aqueous Acidic Media

Electron transfer reaction of theobromine (hereafter referred to as TB) and permanganate ion has been studied using spectrophotometric technique under pseudo first-order conditions at T = 24, [H+] = 3.2 × 10–1 mol dm–3and I = 1.0 mol dm–3 (Na2SO4). Stoichiometric study depicted that two moles of TB were consumed by one mole of permanganate ion. The rate of the reaction is first order in both [TB] and [MnO4-] and second order overall. It was observed that, [H+] and ionic strength respectively enhanced the rate of the reaction in the range studied. Michaelis-Mentens analysis showed no evidence of intermediate complex formation. Added anions and cations were observed to catalyze the reaction rate. The reaction conforms to the rate law as shown below: -d [MnO4-]/dt = (a+b [H+]) [TB] [MnO4-] where a = 0.041 dm3mol–1 s–1 and b= 0.028 dm3mol–1 s–1. The reaction thus occurs by an outer-sphere pathway and plausible mechanism is proposed for the reaction.

Theoretical Insight into Oxidation of Anilines to Azobenzenes Catalyzed by Hexamolybdate: Outer-Sphere Electron and Proton Transfer

Recently, the catalytic activity of Lindqvist-type hexamolybdate [Mo6O19]2– in the oxidation of an aniline derivative (LPhNH2, L = substituent) was demonstrated by Wei and co-workers (Angew. Chem. Int. Ed. 2021, 60, 6382–6385). Herein, taking phenylamine (PhNH2) oxidation to azobenzene (PhNNPh) as a model reaction, we report the density functional theory investigation of the catalytic mechanism of [Mo6O19]2– and illustrate the critical experimental phenomena. During the catalytic reaction, once the preassociation of [Mo6O19]2– and PhNH2 takes place, electron transfer and proton transfer immediately proceed to form an N radical intermediate. The higher the highest occupied molecular orbital energy of the substrate, the easier the formation of the N radical intermediate. The N–N bond formation proceeds via the second PhNH2 nucleophilic attack on the N radical intermediate. The substituent position and the N reaction site of the substrate have a significant effect on the second PhNH2 nucleophilic attack process. In the reaction process, the six MoVI of [Mo6O19]2– are still hexacoordinated, which is defined as the outer-sphere pathway. One of the factors determining the product selectivity is the electrostatic repulsion between LPhNH2 and the N radical intermediate. The experiment reveals that the product yield is increased by the addition of Na2S2O3, while the catalytic reaction is completely deactivated with Na2CO3 or K3PO4. Based on the proposed mechanism, the experimental observation was rationalized. The S2O32– part of Na2S2O3 has a similar function as the electron-withdrawing substituent due to its low lowest unoccupied molecular orbital (LUMO) energy, which reduces the LUMO energy of the N radical intermediate and thus facilitates PhNH2 nucleophilic attack, while the CO32– part of Na2CO3 or PO43– part of K3PO4 has an undesirable effect on the electrophilicity of the N radical intermediate, resulting in the interruption of the catalytic reaction. This work would provide a detailed understanding of the catalytic reaction.

Mechanism of Pd/Senphos-Catalyzed trans-Hydroboration of 1,3-Enynes: Experimental and Computational Evidence in Support of the Unusual Outer-Sphere Oxidative Addition Pathway.

The reaction mechanism of the Pd/Senphos-catalyzed trans-hydroboration reaction of 1,3-enynes was investigated using various experimental techniques, including deuterium and double crossover labeling experiments, X-ray crystallographic characterization of model reaction intermediates, and reaction progress kinetic analysis. Our experimental data are in support of an unusual outer-sphere oxidative addition mechanism where the catecholborane serves as a suitable electrophile to activate the Pd0-bound 1,3-enyne substrate to form a Pd-η3-π-allyl species, which has been determined to be the likely resting state of the catalytic cycle. Double crossover labeling of the catecholborane points toward a second role played by the borane as a hydride delivery shuttle. Density functional theory calculations reveal that the rate-limiting transition state of the reaction is the hydride abstraction by the catecholborane shuttle, which is consistent with the experimentally determined rate law: rate = k[enyne]0[borane]1[catalyst]1. The computed activation free energy ΔG‡ = 17.7 kcal/mol and KIE (kH/kD = 1.3) are also in line with experimental observations. Overall, this work experimentally establishes Lewis acids such as catecholborane as viable electrophilic activators to engage in an outer-sphere oxidative addition reaction and points toward this underutilized mechanism as a general approach to activate unsaturated substrates.

Versatile Utility of Cp*Co(III) Catalysts in C–H Amination under Inner- and Outer-Sphere Pathway

AbstractThis Account describes the recent advances in our research program toward the development of cobalt-catalyzed C–H amidation reactions. In particular, synthetic versatilities of obtainable amino products shown to be achieved on the basis of two distinctive mechanistic scaffolds; inner- and outer-sphere pathways. It highlights our approaches to transit the modes of C–N bond formation by introduction of bidentate LX-type ligands into Cp*Co(III) precursors, thereby broadly expanding the scope of amination reactions.1 Introduction2 Cp*Co-Catalyzed Inner-Sphere C–H Amidation3 Cp*Co-Catalyzed Outer-Sphere C–H Amidation3.1 C(sp2)–N Bond Formation3.2 C(sp3)–N Bond Formation4 Conclusion

Mechanism of Alkyne Hydroarylation Catalyzed by (P,C)-Cyclometalated Au(III) Complexes.

Over the last 5-10 years, gold(III) catalysis has developed rapidly. It often shows complementary if not unique features compared to gold(I) catalysis. While recent work has enabled major synthetic progress in terms of scope and efficiency, very little is yet known about the mechanism of Au(III)-catalyzed transformations and the relevant key intermediates have rarely been authenticated. Here, we report a detailed experimental/computational mechanistic study of the recently reported intermolecular hydroarylation of alkynes catalyzed by (P,C)-cyclometalated Au(III) complexes. The cationic (P,C)Au(OAcF)+ complex (OAcF = OCOCF3) was authenticated by mass spectrometry (MS) in the gas phase and multi-nuclear NMR spectroscopy in solution at low temperatures. According to density functional theory (DFT) calculations, the OAcF moiety is κ2-coordinated to gold in the ground state, but the corresponding κ1-forms featuring a vacant coordination site sit only slightly higher in energy. Side-on coordination of the alkyne to Au(III) then promotes nucleophilic addition of the arene. The energy profiles for the reaction between trimethoxybenzene (TMB) and diphenylacetylene (DPA) were computed by DFT. The activation barrier is significantly lower for the outer-sphere pathway than for the alternative inner-sphere mechanism involving C-H activation of the arene followed by migratory insertion. The π-complex of DPA was characterized by MS. An unprecedented σ-arene Au(III) complex with TMB was also authenticated both in the gas phase and in solution. The cationic complexes [(P,C)Au(OAcF)]+ and [(P,C)Au(OAcF)(σ-TMB)]+ stand as active species and off-cycle resting state during catalysis, respectively. This study provides a rational basis for the further development of Au(III) catalysis based on π-activation.

A Critical Reassessment of the Mechanism of the Oxygen Reduction Reaction on Au(poly) in Aqueous Alkaline Electrolytes

The oxygen reduction reaction, ORR, in aqueous electrolytes, may rank among the most studied heterogeneous electron transfer processes. Despite the extraordinary efforts of numerous research groups worldwide, critical questions still remain unanswered regarding critical aspects of this technologically important reaction and the dependence of its mechanism and rates on the nature of the electrode material. In their pioneering studies, Zurilla et al.1 examined the ORR on polycrystalline gold, Au(poly), in alkaline solutions, using rotating ring-disk electrode, RRDE, techniques. According to these authors, the experimental evidence collected was consistent with a mechanism involving an initial one-electron transfer to yield adsorbed superoxide ion, O2 -(ads), which, subsequently, underwent a second order heterogeneous dismutation generating solution phase peroxide and oxygen, O2(aq) and HO2 -(aq). The same mechanism was later invoked by Adzic et al.2 for the ORR on Au(100), a surface that displayed extraordinary activity compared to other low index faces of Au. More recently, Ignaczak et al.3 put forward theoretical arguments that support the view that the initial RDS is actually of the outer sphere type, yielding a solvated species, i.e. O2 -(aq), which is then followed by a subsequent, fast, outer sphere one electron-transfer, generating solution phase peroxide, HO2 -(aq), and not by a second order dismutation of as was postulated earlier in the literature. This is shown as the ‘outer sphere pathway’ in Scheme 1. Scheme 1: Proposed inner and outer sphere pathways for ORR on Au in basic solution.This presentation will describe the use of RRDE methods to examine the kinetics of the ORR on Au(poly) in 0.1 M NaOH + 0.9 M NaClO4 aqueous electrolytes containing oxygen in one case and peroxide in the other. The results obtained were found to be consistent with Ignaczak et al.’s mechanism, or equivalently an inner sphere pathway (Scheme 1) which includes a fast equilibrium between O2 -(aq), HO2 -(aq) and their corresponding adsorbed counterparts, O2 -(ads) i.e. and HO2 -(ads) however, a critical assessment of in situ vibrational spectroscopy data published in the literature has raised questions regarding the assignment of the spectral features reported for these adsorbed species. Also considered in this model is the direct reduction of HO2 -(aq) and O2(aq) to generate OH-(aq). Quantitative analyses of data collected in O2-saturated and Ar-purged containing solutions made it possible to determine a unique set of kinetic rate constants for the various steps in the proposed mechanism over a wide potential range.

Rapid formation of Csp3–Csp3 bonds through copper-catalyzed decarboxylative Csp3–H functionalization

Transition-metal-catalyzed decarboxylative and CH functionalization strategy for the construction of Csp2-Csp2, Csp2-Csp, and Csp2-Csp3 bonds has been extensively studied. However, research surveys of this synthetic strategy for the Csp3-Csp3 bond forming reactions are surprisingly scarce. Herein, we present an efficient approach for the rapid formation of Csp3–Csp3 bond through copper-catalyzed decarboxylative Csp3–H functionalization. The present method should provide a useful access to C3-substituted indole scaffolds with possible biological activities. Mechanistic experiments and DFT calculations supported a dual-Cu(II)-catalytic cycle involving rate-determining decarboxylation in an outer-sphere radical pathway and spin-crossover-promoted CC bond formation. This strategy offers a promising synthesis method for the construction of Csp3–Csp3 bond in the field of synthetic and pharmaceutical chemistry and extends the number of still limited copper-catalyzed decarboxylative Csp3–Csp3 bond forming reaction.

Computational Insights into Palladium/Boron-Catalyzed Allylic Substitution of Vinylethylene Carbonates with Water: Outer-Sphere versus Inner-Sphere Pathway and Origins of Regio- and Enantioselectivities

Computational Insights into Palladium/Boron-Catalyzed Allylic Substitution of Vinylethylene Carbonates with Water: Outer-Sphere versus Inner-Sphere Pathway and Origins of Regio- and Enantioselectivities

MnSOD functions as a thermoreceptor activated by low temperature

A conservative characteristic of manganese superoxide dismutase is the rapid formation of product inhibition at high temperatures. At lower temperatures, the enzyme is less inhibited and undergoes more catalytic fast cycles before being product-inhibited. The temperature-dependent kinetics could be rationalized by the temperature-dependent coordination in the conserved center of manganese superoxide dismutase. As temperature decreases, a water molecule (WAT2) approaches or even coordinates Mn as the sixth ligand to interfere with O2•--Mn coordination and reduce product inhibition, so the dismutation should mainly proceed in the fast outer-sphere pathway at low temperatures. Cold-activation is an adaptive response to low temperature rather than a passive adaptation to excess superoxide levels since the cold-activated dismutase activity significantly exceeds the amount of superoxide in the cell or mitochondria. Physiologically speaking, cold activation of manganese superoxide dismutase mediates cold stress signaling and transduces temperature (physical signal) degree into H2O2 fluxes (chemical signal), which in turn may act as a second messenger to induce a series of physiological responses such as cold shock.

Ir/f-Ampha complex catalyzed asymmetric sequential hydrogenation of enones: a general access to chiral alcohols with two contiguous chiral centers.

A general and highly efficient method for asymmetric sequential hydrogenation of α,β-unsaturated ketones has been developed by using an iridium/f-Ampha complex as the catalyst, furnishing corresponding chiral alcohols with two contiguous stereocenters in high yields with excellent diastereo- and enantioselectivities (up to 99% yield, >20 : 1 dr and >99% ee). Control experiments indicated that the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C and CO bonds of the enones were hydrogenated sequentially, and the final stereoselectivities were determined by the dynamic kinetic resolution of ketones. Moreover, DFT calculations revealed that an outer sphere pathway was involved in both reduction of CC and CO bonds of enones. The synthetic utility of this method was demonstrated by a gram-scale reaction with very low catalyst loading (S/C = 20 000) and a concise synthetic route to key chiral intermediates of the antiasthmatic drug CP-199,330.

KINETICS AND MECHANISM OF THE OXIDATION OF L-ASCORBIC ACID BY POTASSIUM TRISOXALATOFERRATE (III) TRIHYDRATE IN AQUEOUS HYDROCHLORIC ACID MEDIUM

The kinetics of the oxidation of K3[Fe(C2O4)3].3H2O by L-ascorbic acid has been studied in aqueous acidic medium. The stoichiometric studies showed that 1 mole of H2A was oxidized for every 2 moles of Fe(C2O4)33- reduced. Under pseudo-first order conditions of H2A >> Fe(C2O4)33-, the reaction was found to have first order dependence on each of the reactants, giving second order overall. The reaction rate was found to be directly dependent on acid concentration and increased with increase in ionic strength of reaction system. It was also evident that increase in dielectric constant of the reaction medium (D) enhanced the reaction rate and addition of CH3COO-, HCOO-, Mg2+and Li+ catalyzed the rate of the reaction. The oxidation of L-ascorbic acid by potassium trisoxalatoferrate (III) trihydrate is rationalized in terms of absence of ion pair complex formation with outer-sphere reaction pathway characteristics.

Mechanism and Selectivities in Ru-Catalyzed Anti-Markovnikov Formal Hydroalkylation of 1,3-Dienes and Enynes: A Computational Study.

The mechanism of the Ru(II)-catalyzed anti-Markovnikov formal hydroalkylation of 1,3-dienes and enynes by hydrazones has been elucidated using density functional theory (DFT) calculations. Our results indicate that the C-C bond formation proceeds through a highly polar outer-sphere transition state (TS) stabilized by the THF solvent, not the ordered inner-sphere TS as originally proposed. The regioselectivity for 1,2-anti-Markovnikov addition is primarily due to the formation of an extensively π-conjugated intermediate after the nucleophilic attack on the 1-position of the diene. The stability of this intermediate means that nucleophilic attack at the 1-position is able to utilize the outer-sphere pathway, while attacks on all other positions of the diene must proceed through more crowded and less-favorable inner-sphere TSs. We show that the electronics of substituents on the hydrazone and the diene have a significant impact on the C-C formation barrier, which rationalizes the limitations on the substrate scope. The preferred coordination sphere around Ru(II) and the rigidity of the reacting substrates lead to a sterically demanding TS geometry, which explains the sensitivity of the reaction to the ligand size.

Mechanism-Guided Development of Transition-Metal-Catalyzed C-N Bond-Forming Reactions Using Dioxazolones as the Versatile Amidating Source.

Catalytic reactions that construct carbon-nitrogen bonds are one of central themes in both synthetic and medicinal chemistry since the obtainable nitrogen-containing motifs are commonly encountered in natural products and have also seen a growing prominence as key structural features in marketed drugs and preclinical candidates. Pd-catalyzed cross-couplings, such as Buchwald-Hartwig amination, are at the forefront of such synthetic methods in practical settings. However, they require prefunctionalized substrates such as (hetero)aryl halides that must be prepared independently, often by multiple operations. One emerging way to circumvent these preparatory steps and directly convert ubiquitous C-H bonds into valuable C-N bonds is catalytic C-H amination, which allows synthetic chemists to devise shorter and more efficient retrosynthetic schemes. The past two decades have witnessed considerable progress in expanding the repertoire of this strategy, especially by identifying effective amino group precursors. In this context, dioxazolones have experienced a dramatic resurgence in recent years as a versatile nitrogen source in combination with transition-metal catalyst systems that facilitate decarboxylation to access key metal-acylnitrenoid intermediates. In addition to their high robustness and easy accessibility from abundant carboxylic acids, the unique reactivity of the transient intermediates in the amido group transfer has led to a fruitful journey for mild and efficient C-H amidation reactions.This Account summarizes our recent contributions to the development of C-N bond-forming reactions using dioxazolones as effective nitrenoid precursors, which are categorized into two subsets according to their mechanistic differences: inner- versus outer-sphere pathways. The first section describes how we could unveil the synthetic potential of dioxazolones in the realm of the inner-sphere C-H amidation, where we demonstrated that dioxazolones serve not only as manageable alternatives to acyl azides but also as highly efficient reagents to significantly reduce the catalyst loading and temperature. Taking advantage of the mild conditions in combination with group 9 Cp*M complexes (M = Rh, Ir, Co) or isoelectronic Ru species, we have dramatically expanded the accessible synthetic scope. Mechanistic investigations revealed that the putative metal-nitrenoid species is involved as a key intermediate during catalysis, which leads to facile C-N bond formation. On the basis of the mechanistic underpinning, we have succeeded in developing novel catalytic platforms that harness the intermediacy of metal-nitrenoids to explore C-H insertion chemistry via an outer-sphere pathway. Indeed, the tailored catalysts were capable of suppressing the competitive Curtius-type decomposition, thus granting access to versatile lactam products. We have further repurposed the catalytic systems upon modification of chelating ligands and also the identity of the transition metal to achieve three goals: (i) addressing selectivity issues to control the regio-, chemo-, and enantioselectivities, (ii) developing sustainable catalysis by first-low metals, and (iii) navigating chemical space for (di)functionalization of alkenes/alkynes. Together with our own research efforts, highlighted herein are some important relevant advances by other groups. We finally conclude with a brief overview with an eye toward further developments.

Kinetic Analysis of Electrochemical Lactonization of Ketones Using Water As the Oxygen Atom Source

Lactones serve as key synthetic intermediates for the large-scale production of several important chemicals, such as polymers, pharmaceuticals, and scents. Current thermochemical methods for the formation of some lactones rely on molecular oxidants, which yield stoichiometric side products that result in a poor atom economy and impose safety hazards when in contact with organic substrates and solvents. Electrochemical synthesis can alleviate these concerns by exploiting an applied potential to enable the possibility of a clean and safe route for lactonization. In this study, we investigated the mechanism of electrochemical lactone formation from cyclic ketones. When using a platinum anode and cathode in acetonitrile with 10 M H2O and 400 mM cyclohexanone, we found that non-Baeyer-Villiger products, δ-hexanolactone and ɣ-caprolactone, are formed with a total Faradaic efficiency of ~20%. Isotope labeling experiments support that water is the oxygen atom source for this reaction. In addition, electrochemical kinetic data suggest a 1st order dependence on water at low water concentrations (<2 M H2O) and a 0th order dependence on the substrate, cyclohexanone. A Tafel slope of 139 mV/decade was measured at 400 mM cyclohexanone and 10 M H2O, implying an initial electron transfer as the rate determining step. Literature proposed mechanisms for similar transformations suggest an outer sphere pathway. However, based on the collected electrochemical kinetic data, we propose the possibility that Pt reacts with water in an initial electron transfer that forms Pt-OH, which can subsequently react with the ketone substrate. A subsequent electron transfer forms a ring opened carboxylic acid cation that can reclose to form either of the observed five- or six-member ring lactone products.

Mechanistic elucidation of the role of metal oxidation states in nickel mediated electrocatalytic coupling of benzyl halides

We present the mechanistic understanding of an electrochemically-driven nickel-catalyzed coupling reaction. Computational analysis reveals that the spin density is mostly residing on the nickel (Ni) center when NiII is reduced to NiI. Ni-mediated halogen atom abstraction through outer-sphere electron-transfer pathway to yield coupling products under mild conditions is demonstrated. Importantly, we have elucidated the role of NiI and Ni0 for successive coupling of benzyl bromide and benzyl chloride derivatives, respectively, to corresponding bibenzyl products. The Ni-catalyst bearing a PN3P-ligand is an effective catalyst, producing a strong ligand effect on the reactivity and selectivity for the homocoupling reactions.

A Mechanistic Analysis of the Palladium-Catalyzed Formation of Branched Allylic Amines Reveals the Origin of the Regio- and Enantioselectivity through a Unique Inner-Sphere Pathway.

A recently reported palladium-catalyzed allylic substitution of vinyl-substituted cyclic carbonates (VCCs) with aryl amines represents a rare example of a regio- and enantioselective synthesis of α,α-disubstituted allylic N-aryl amines. However, the underlying reasons for this unusual selectivity profile remain elusive. In the present work, density functional theory (DFT) calculations in combination with mechanistic control experiments were performed to elucidate in detail this allylic amination manifold and the origin of the regio- and enantioselectivity. The combined data show that after oxidative addition of the VCC to Pd0 , the nucleophilic attack via an originally proposed outer-sphere pathway gives, however, the opposite regioisomer compared to the experimental results. Instead, nucleophilic attack of the amine reagent via a unique type of chelation-assisted, inner-sphere pathway accounts for the experimentally observed "branched" regioselectivity and high enantio-control.

Effect of acid and ionic strength on the kinetics of electron transfer reaction of n-(2-hydroxy-ethyl) ethylenediamine-n, n’, n’-triacetatocobaltate (ii) complex with hypochlorite ion in aqueous acidic medium

The influence of acid and ionic strength on the rate of electron transfer reaction of N-(2-hydroxy-ethyl)ethylenediamine-N,N’,N’-triacetatocobaltate(II)(hereafter, complex with Hypochlorite ion in aqueous nitric acid medium have been studied at I = 0.2 mol dm-3(NaNO3), [H+] = 1 × 10-2 mol dm-3, , T = 300 ± 1 K and λmax = 525 nm. Stoichiometric study showed 1:1 `mole ratio. The rate law derived from the kinetic study under pseudo first order condition is . The rate constant of reaction,  varies inversely with acid concentration, [H+]. The overall rate law is therefore represented as: . The reaction displayed positive salt effect which suggests the activated complex was made up of similar charged species. The reaction was catalysed by addition of formate, HCOO- and potassium, K+ ions and the Michaelis-Menten’s plot gave zero intercept indicating the absence of intermediate complex. A reaction mechanism via an outer-sphere pathway is proposed for this reaction. Â

Kinetics of oxidation of ethylenediammine-N,N,N’,N’-tetraacetatocobaltate(II)complex by silver-activated persulphate ion in aqueous acidic medium

The kinetics of oxidation of Ethylenediammine-N,N,N’,N’-tetraacetatocobaltate(II) complex ([Co(II)EDTA2-]) by silver-activated persulphate ion in a ueous nitric acid medium was studied at I = 0.5 mol dm-3(NaNO3), [H+] = 1 × 10-2 mol dm-3, [Ag+] = 1 × 10-2 mol dm-3, T = 299 ± 1 K and λmax = 520 nm. Stoichiometric study showed 2:1 (Reductant: Oxidant) mole ratio. The reaction exhibited first order with respect to the [Co(II)EDTA2-] and [ S2O82-] and the rate constant, (5.90 × 10-2 dm3mol-1s-1) was independent of the acid concentration, but varied linearly with catalyst concentration, [Ag+]. The overall rate law is represented as: d[Co(II)EDTA2-]/dt = 5.90 x 10-2 [Ag+][Co(II)EDTA2-][s2082-] The reaction displayed zero salt effect suggesting an activated complex composed of either a neutralcharged, neutral-neutral reactant species or ion-pair. The reaction was catalysed by addition of formate ion, HCOO- and the Michaelis-Menten’s type plot gave zero intercept indicating the absence of intermediate complex. Also, the activation enthalpy ( △H# = +39.27 kJ mol-1) and entropy ( △H# = -136.73 J K-1 mol-1) were determined. The entropy of activation shows a more ordered activated complex relative to the reactants species. Evaluating the experimental data, an outer-sphere mechanistic pathway via ion pair activated complex is proposed for the reaction.Keywords: Kinetics, Oxidation, Aminocarboxylactocobaltate(II), Persulphate ion