First‐principle calculations on CO oxidation catalyzed by a gold nanoparticle

We have elucidated the mechanism of CO oxidation catalyzed by gold nanoparticles through first‐principle density‐functional theory (DFT) calculations. Calculations on selected model show that the low‐coordinated Au atoms of the Au₂₉ nanoparticle carry slightly negative charges, which enhance the O₂ binding energy compared with the corresponding bulk surfaces. Two reaction pathways of the CO oxidation were considered: the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH). The overall LH reaction O_2(ads) + CO_(gas) → O_2(ads) + CO_(ads) → OOCO_(ads) → O_(ads) + CO_2(gas) is calculated to be exothermic by 3.72 eV; the potential energies of the two transition states ( TS_LH1 and TS_LH2 ) are smaller than the reactants, indicating that no net activation energy is required for this process. The CO oxidation via ER reaction Au₂₉ + O_2(gas) + CO_(gas) → Au₂₉–O_2(ads) + CO_(gas) → Au₂₉–CO_3(ads) → Au₂₉–O_(ads) + CO_2(gas) requires an overall activation barrier of 0.19 eV, and the formation of Au₂₉–CO_3(ads) intermediate possesses high exothermicity of 4.33 eV, indicating that this process may compete with the LH mechanism. Thereafter, a second CO molecule can react with the remaining O atom via the ER mechanism with a very small barrier (0.03 eV). Our calculations suggest that the CO oxidation catalyzed by the Au₂₉ nanoparticle is likely to occur at or even below room temperature. To gain insights into high‐catalytic activity of the gold nanoparticles, the interaction nature between adsorbate and substrate is also analyzed by the detailed electronic analysis. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Does enhanced oxygen activation always facilitate CO oxidation on gold clusters?

We investigate the catalytic activity of the subnanometer‐sized bimetallic Au₁₉Pt cluster for oxidation of CO via first‐principles density functional theory calculations. For this purpose we consider two structurally similar and energetically close homotops of the Au₁₉Pt cluster with the Pt atom occupying an edge (Td‐E) or a facet (Td‐S) site of a 20‐atom tetrahedron. Using these homotops as catalysts we calculate the complete reaction paths and the thermodynamic functions corresponding to the oxidation of CO to CO₂. It is found that the oxidation of CO on the Td‐S isomer occurs through a smaller reaction barrier (0.38 eV) as compared with that on the Td‐E isomer (0.70 eV), although the activation of O₂ on the latter is much higher than that on the former. Therefore, a clear conclusion is that a higher O₂ activation, which is generally believed to be the key factor for CO oxidation, solely cannot determine the catalytic efficiency of the Au‐Pt bimetallic clusters. In addition, we find a stronger CO adsorption on the Td‐E isomer (2.06 eV) as compared with that on the Td‐S isomer (1.68 eV). Although stronger CO adsorption on the Td‐E isomer leads to a higher O₂ activation; however, high value of CO adsorption energy deteriorates the catalytic activity of the Td‐E isomer towards the CO oxidation reaction. © 2015 Wiley Periodicals, Inc.     

Hydrothermal Syntheses and Crystal Structures of Two New Heteropolyoxovanadoborates Containing {(VO)<Subscript>12</Subscript>O<Subscript>6</Subscript>[B<Subscript>3</Subscript>O<Subscript>6</Subscript>(OH)]<Subscript>6</Subscript>(H<Subscript>2</Subscript>O)} Cluster

Two new heteropolyoxovanadoborates (H₂dap)₂H₆{(VO)₁₂O₆[B₃O₆(OH)]₆(H₂O)}·13H₂O (1, dap = 1,2-diaminopropane) and {[Zn(dien)]₂[Zn(dien)(H₂O)]₄(VO)₁₂O₆[B₃O₆(OH)]₆(H₂O)}₂·15H₂O (2, dien = diethylenetriamine) have been hydrothermally synthesized and structurally characterized. Both 1 and 2 contain {(VO)₁₂O₆[B₃O₆(OH)]₆(H₂O)} cluster (denoted on V₁₂B₁₈), which is constructed by a puckered B₁₈O₃₆(OH)₆ ring sandwiched between two triangles of six alternating cis and trans edge-sharing vanadium atoms, and a central water molecule. 1 consists of discrete [V₁₂B₁₈]¹⁰⁻ cluster anions with H₂dap²⁺ as counterions, while 2 consists of discrete neutral {[Zn(dien)]₂[Zn(dien)(H₂O)]₄[V₁₂B₁₈]} clusters, which are built from two types of zinc(II) complex fragments connecting with V₁₂B₁₈ cluster through two Zn-(μ ₃-O)-B bonds. Interestingly, 2 is the only example of the V₁₂B₁₈ cluster decorated by two types of zinc(II) complex fragments.     

Mechanism of CO Oxidation on Cu2O (111) Surface: A DFT and Microkinetic Study

Catalytic oxidation has been recognized as one of the most efficient and promising techniques for the abatement of CO and volatile organic compounds. In the present work, the CO oxidation mechanism on perfect Cu₂O (111) surface was investigated by using density functional theory (DFT) calculations with the periodic surface model. The unsaturated singly coordinated Cu⁺ site of Cu₂O (111) surface could effectively adsorb gaseous CO molecule with a strong adsorption energy of −1.558 eV. The adsorbed O on Cu₂O (111) surface is very active toward CO oxidation with only 0.269 eV energy barrier. The reaction between CO and lattice O is the rate‐determining step of Mars‐van‐Krevelen (MvK) type CO oxidation with the energy barrier of 1.629 eV. The CO oxidation cycle initiated by the reaction between coadsorbed CO and O₂ at the Cu_I site has a relatively lower energy barrier of 1.082 eV and is, therefore, more likely to proceed compared with the MvK cycle. Microkinetic rate constants of elementary reaction steps based on the transition state theory were deduced, which could be helpful in the kinetic modeling of CO oxidation on Cu₂O surface.     

Structure and surface properties of ZrO<Subscript>2</Subscript>, CeO<Subscript>2</Subscript>, and Zr<Subscript>0.5</Subscript>Ce<Subscript>0.5</Subscript>O<Subscript>2</Subscript> prepared by a microemulsion method according to X-ray diffraction,TPR, and EPR data

It was established by X-ray diffraction, TPR, and EPR that microemulsion (m.e.) synthesis yields the binary oxides ZrO₂(m.e.) and CeO₂(m.e.) and the mixed oxide Zr_0.5Ce_0.5O₂(m.e.) in the form of a tetragonal, cubic, and pseudocubic phase, respectively, having crystallite sizes of 5–6 nm. The bond energy of surface oxygen in the (m.e.) samples is lower than in their analogues prepared by pyrolysis. Hydrogen oxidation on the oxides under study occurs at higher temperatures than CO oxidation. ZrO₂(m.e.) and CeO₂(m.e.) are active in O₂⁻ formation during NO + O₂ adsorption, while CeO₂ is active during CO + O₂ adsorption, too. However, its amount here is one-half to one-third its amount in the pyrolysis-prepared samples, signifying a reduced number of active sites, which are Zr⁴⁺ and Ce⁴⁺ coordinatively unsaturated cations and Me⁴⁺-O²⁻ pairs. O₂⁻ radical anions are stabilized in the coordination sphere of Zr⁴⁺ coordinatively unsaturated cations via ionic bonding, and in the sphere of Ce⁴⁺ cations, via covalent bonding. Ionic bonds are stronger than ionic-covalent bonds and do not depend on the ZrO₂ phase composition. Zr_0.5Ce_0.5O₂ is inactive in these reactions because of the strong interaction of Zr and Ce cations. It is suggested that Ce^{(4 + β)+} coordinatively unsaturated cations exist on its surface, and their acid strength is lower than that of Zr⁴⁺ and Ce⁴⁺ cations in ZrO₂ and CeO₂, according to the order ZrO₂ > CeO₂ ≥ Zr_0.5Ce_0.5O₂. Neither TPR nor adsorption of probe molecules revealed Zr cations on the surface of the mixed oxide.     

Structure Sensitivity of CO Oxidation on Co3O4: A DFT Study

The reaction mechanism of CO oxidation on the Co₃O₄ (110) and Co₃O₄ (111) surfaces is investigated by means of spin‐polarized density functional theory (DFT) within the GGA+U framework. Adsorption situation and complete reaction cycles for CO oxidation are clarified. The results indicate that 1) the U value can affect the calculated energetic result significantly, not only the absolute adsorption energy but also the trend in adsorption energy; 2) CO can directly react with surface lattice oxygen atoms (O_2f/O_3f) to form CO₂ via the Mars–van Krevelen reaction mechanism on both (110)‐B and (111)‐B; 3) pre‐adsorbed molecular O₂ can enhance CO oxidation through the channel in which it directly reacts with molecular CO to form CO₂ [O₂(a)+CO(g)→CO₂(g)+O(a)] on (110)‐A/(111)‐A; 4) CO oxidation is a structure‐sensitive reaction, and the activation energy of CO oxidation follows the order of Co₃O₄ (111)‐A(0.78 eV)>Co₃O₄ (111)‐B (0.68 eV)>Co₃O₄ (110)‐A (0.51 eV)>Co₃O₄ (110)‐B (0.41 eV), that is, the (110) surface shows higher reactivity for CO oxidation than the (111) surface; 5) in addition to the O_2f, it was also found that Co³⁺ is more active than Co²⁺, so both O_2f and Co³⁺ control the catalytic activity of CO oxidation on Co₃O₄, as opposed to a previous DFT study which concluded that either Co³⁺ or O_2f is the active site.     

Self-Organization of a Binuclear Ruthenium Complex to Tetra- and Octanuclear Catalysts for Water Oxidation for “Artificial Photosynthesis”

The kinetics and mechanism of the action of tetra- and octanuclear ruthenium catalysts for water oxidation with Ce(IV) compounds in “artificial photosynthesis” have been studied. These catalysts are formed from a complex K₄[Ru₂(SO₄)₂(μ-SO₄)₂(μ-O)₂] · 2H₂O in an acidic medium via its self-organization. A tetranuclear adamantane-like cluster Ru₄O₆ is obtained during the dimerization of a binuclear complex and catalyzes the four-electron water oxidation to an oxygen molecule. An octanuclear cluster Ru₈O₁₂ is formed during the tetramerization of a binuclear complex and catalyzes the eight-electron water oxidation to an oxozone molecule O₄, which readily splits to two oxygen molecules.     

Reducing the Cost and Preserving the Reactivity in Noble‐Metal‐Based Catalysts: Oxidation of CO by Pt and Al–Pt Alloy Clusters Supported on Graphene

The oxidation mechanisms of CO to CO₂ on graphene‐supported Pt and Pt‐Al alloy clusters are elucidated by reactive dynamical simulations. The general mechanism evidenced is a Langmuir–Hinshelwood (LH) pathway in which O₂ is adsorbed on the cluster prior to the CO oxidation. The adsorbed O₂ dissociates into two atomic oxygen atoms thus promoting the CO oxidation. Auxiliary simulations on alloy clusters in which other metals (Al, Co, Cr, Cu, Fe, Ni) replace a Pt atom have pointed to the aluminum doped cluster as a special case. In the nanoalloy, the reaction mechanism for CO oxidation is still a LH pathway with an activation barrier sufficiently low to be overcome at room temperature, thus preserving the catalyst efficiency. This provides a generalizable strategy for the design of efficient, yet sustainable, Pt‐based catalysts at reduced cost.     

Ruthenium Carbonyl Cluster Complexes with Phenylgermyl Ligands from the Reactions of Ph<Subscript>3</Subscript>GeH with Ru(CO)<Subscript>5</Subscript> and Ru<Subscript>3</Subscript>(CO)<Subscript>12</Subscript>

Four new triphenylgermylruthenium carbonyl compounds HRu(CO)₄GePh₃, 14; Ru(CO)₄(GePh₃)₂, 15; Ru₂(CO)₈(GePh₃)₂, 16; and Ru₃(CO)₉(GePh₃)₃(μ-H)₃, 17 were obtained from the reaction of Ru(CO)₅ with Ph₃GeH in hexane solvent at reflux, 68 °C. The major product 14 was formed by loss of CO from the Ru(CO)₅ and an oxidative addition of the GeH bond of the Ph₃GeH to the metal atom. This six coordinate complex contains one terminal hydrido ligand. Compound 15 is formed from 14 and contains two trans-positioned GePh₃ ligands in the six coordinate complex. Compound 16 contains two Ru(CO)₄(GePh₃) fragments joined by an Ru–Ru single bond. Compound 17 contains a triangular cluster of three ruthenium atoms with three bridging hydrido ligands and one terminal GePh₃ ligand on each metal atom. When heated to 125 °C, 14 was converted to the new triruthenium compound Ru₃(CO)₁₀(μ-GePh₂)₂, 18. Compound 18 consists of a triangular tri-ruthenium cluster with two GePh₂ ligands bridging two different edges of the cluster and one bridging CO ligand. Ru₃(CO)₁₂ was found to react with Ph₃GeH at 97 °C to yield three products: 15, and two new compounds Ru₃(CO)₉(μ-GePh₂)₃, 19 and Ru₂(CO)₆(μ-GePh₂)₂(GePh₃)₂, 20 were obtained. Compound 19 is similar to 18 having a triangular tri-ruthenium cluster but has three bridging GePh₂ ligands, one on each Ru–Ru bond. Compound 20 contains only two ruthenium atoms joined by a single Ru–Ru bond that has two bridging GePh₂ ligands and a terminal GePh₃ ligand on each metal atom. All compounds were characterized by a combination of IR, ¹H NMR, single-crystal X-ray diffraction analyses. This report is dedicated to Professor Dieter Fenske on the occasion of his 65th birthday for his many pioneering contributions to the chemistry of metal chalcogenide cluster complexes.     

Strain boosts CO oxidation on Ni single-atom-catalyst supported by defective graphene

In order to realize the sulfur and water resistance and facilitate the CO oxidation reactions,the effects of strain on the adsorption of CO,O₂,SO₂ and H₂O molecules on Ni single-atom-catalyst supported by single-carbon-vacancy graphene(Ni-SG) have been studied based on first principles calculations.It shows that the compressive strain increases the adsorption energies of all above mentioned molecules on Ni-SG,where SO₂ is adsorbed more strongly on Ni-S...     

Theoretical investigation for the reaction of N<Subscript>2</Subscript>O with CO catalyzed by Pt-Graphene

To find an efficient catalyst to catalytic conversion of hazardous gases maybe the important way for solving environmental problems. We performed the first-principles density functional theory (DFT) to investigate the CO oxidation by using N₂O as an oxidizing agent over an Pt-Graphene catalyst. The results indicated that CO oxidation by N₂O on Pt-Graphene may occur via two pathways: (1) Adsorption of N₂O followed by CO and (2) Adsorption of CO followed by N₂O. Although the CO was more likely to adsorb on the Pt-Graphene than N₂O, but when the Pt site was first covered by the CO, the higher barrier energy (20.28 kcal/mol) would limit the reaction to react. However, the N₂O molecule was first decomposed on the Pt-site yielding the N₂ and O-Pt-Graphene, which was an active species for the CO oxidation. Thus, control of the adsorbing molecules over Pt-Graphene might be a key factor for the activity of the catalyst, and this may open new avenues in searching for oxidation of CO at an economical cost.     

Open Pentaruthenium Cluster Complexes Formed from the Addition of Benzoic Acid to Ru<Subscript>5</Subscript>(C)(CO)<Subscript>15</Subscript>

Two isomers of Ru₅(C)(CO)₁₄(O₂CC₆H₅)(μ-H): Ru₅(C)(CO)₁₄(η²-O₂CC₆H₅)(μ-H), 2 and Ru₅(C)(CO)₁₄(μ-O₂CC₆H₅)(μ-H), 3 were obtained from the reaction of Ru₅(C)(CO)₁₅ with benzoic acid (PhCO₂H). Both compounds were characterized structurally by X-ray diffraction analysis. Compound 2 contains an opened pentaruthenium cluster with a chelating benzoate ligand on the ruthenium atom that was opened. Compound 3 contains an opened pentaruthenium cluster with a benzoate ligand on that bridges a pair of ruthenium atoms which are not mutually bonded. Compound 2 can be converted partially to 3 and 3 partially back to 2 and they form a 1.54/1.0 ratio (3/2) at equilibrium in solution at 95 °C.     

Theoretical study of model elementary reactions of dissociative addition of light hydrocarbons to the Ti-doped aluminide cluster Al<Subscript>12</Subscript>Ti

The potential energy surfaces (PES), energies E, and activation barriers h of elementary reactions of dissociative addition of CH₄ and C₂H₆ molecules to the Al₁₂Ti cluster with a marquee structure in the singlet and triplet states were calculated within the B3LYP approximation of the density functional theory using the 6-31G* basis set. The first stage of the reaction Al₁₂Ti + CH₄ leads to the adsorption complex CH₄ · Al₁₂Ti with the R(TiC) distance of ～2.4 Å. The methane molecule is coordinated as a tridentate ligand the singlet state and as a bidentate ligand in the triplet state, although both coordination modes are close in energy. In the transition state, the CH₄ molecule is coordinated through its active C-H bond to an inclined Ti-Al edge of the cluster, and the C-H bond is significantly elongated and weakened. The activation barrier height h referenced to the CH₄ complex is ～9 and ～19 kcal/mol for the singlet and triplet, respectively, and that referenced to the primary products Al₁₂Ti(CH₃)(H) is ～21 kcal/mol. The barrier to migration of the CH₃ group around the metal cluster is estimated at ～10 kcal/mol. At the initial stage of the reaction Al₁₂Ti + C₂H₆, two types of C₂H₆ · Al₁₂Ti adsorption complexes are formed. In one of them, the ethane molecule is coordinated through a methyl group (as the methane molecule); and in the other type, the coordination is through the C-C bond. This reaction can proceed through two paths by means of insertion into C-H or C-C bonds to give Al₁₂Ti(C₂H₅)(H) or Al₁₂Ti(CH₃)₂, respectively. The second path is impeded by a high barrier (～30 kcal/mol) and is possible, if at all, only at high temperatures. Conversely, the insertion into a C-H bond in ethane is somewhat more favorable than in methane. Analogously, the PES of addition of the second methane molecule to Al₁₂Ti(CH₃)(H) was calculated. The second molecule is adsorbed and dissociates by the same mechanism as the first CH₄ molecule, but with somewhat lower barriers and energy effect of formation of Al₁₂Ti(CH₃)₂(H)₂. The addition of propane and longer hydrocarbons is briefly considered. The results are compared with the results of previous analogous calculations of the PES of related reactions of dissociative adsorption of dihydrogen on the Al₁₂Ti cluster, which are more exothermic, have lower barriers, and can occur under milder conditions.     

Interaction of dioxygen with the platinum Pt19/SnO2/H2 cluster: DFT calculation

The adsorption of the O₂ molecule onto the surface of the Pt₁₉ platinum cluster deposited onto the tin dioxide crystal surface in the presence of dissociated hydrogen molecule has been calculated by the density functional theory method within the generalized gradient approximation (GGA-PBE) with periodic boundary conditions and a projector-augmented plane-wave (PAW) basis set. It has been demonstrated that the oxygen molecule can be adsorbed without a barrier onto the free surface of the Pt₁₉/SnO₂/H₂ cluster to form a superoxy isomer with one Pt-O bond (the energy of elimination of the oxygen molecule is 0.75 eV), which converts almost without a barrier to more stable peroxide isomers with two Pt-O bonds (the energy of elimination of the O₂ molecule is 1.2?1.7 eV). The energy of elimination of the oxygen molecule from the isomers with two-coordinated oxygen positions at the cluster edges is 2.10?2.53 eV. The isomers with mono- and tricoordinated oxygen positions are less energetically favorable than the isomers with two-coordinated oxygen positions. The process of addition of the oxygen molecule to the platinum cluster and elimination of the water molecule formed in the reaction Pt₁₉/SnO₂/H₂ + O₂ → Pt₁₉/SnO₂/O + H₂O is energetically favorable by 1.6 eV.     

Selective oxidation of carbon monoxide in hydrogen-containing gas on CuO-CeO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts prepared by surface self-propagating thermal synthesis

The CuO-CeO₂/Al₂O₃ catalysts for the selective oxidation of CO in hydrogen-containing mixtures were prepared by surface self-propagating thermal synthesis (SSTS) with the use of cerium nitrate Ce(NO₃)₃, the ammonia complex of copper acetate [Cu(NH₃)₄](CH₃COO)₂, and citric acid C₆H₈O₇ as a fuel additive. The effect of the C₆H₈O₇/Ce(NO₃)₃ molar ratio on the catalyst activity and selectivity for oxygen was studied. The catalyst samples were studied by X-ray diffraction (XRD) analysis, temperature-programmed reduction (TPR-H₂), IR spectroscopy of adsorbed CO, and transmission electron microscopy (TEM). It was found that an increase in the C₆H₈O₇/Ce(NO₃)₃ ratio resulted in an increase in the degree of dispersion of the resulting CeO₂ phase. The greatest amount of dispersed CuO particles, which are responsible for catalytic activity in the oxidation of CO, was formed at C₆H₈O₇/Ce(NO₃)₃ = 1.     

Effect of CeO<Subscript>2</Subscript> on the properties of the Pd/Co<Subscript>3</Subscript>O<Subscript>4</Subscript>/cordierite catalyst in the conversion of CO,NO, and hydrocarbons

The effect of CeO₂ on the properties of the Pd/Co₃O₄-CeO₂/cordierite catalyst is a function of the method of its preparation. The catalyst obtained by the simultaneous deposition of cerium oxide and cobalt oxide showed high activity in the oxidation of CO (CO + O₂, CO + NO) and extensive oxidation of hexane (C₆H₁₄ + O₂). This behavior is due to the increased mobility of surface oxygen and increased dispersion of the catalyst components.     

Conductivity of SnO<Subscript>2</Subscript>-In<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocrystalline composite films

The conductivity of films consisting of a mixture of SnO₂ and In₂O₃ nanocrystals at 200–500°C was studied. Based on the experimental data, it was assumed that in films containing less than 20 wt % In₂O₃, the current flows along SnO₂ nanocrystals. A model of conductivity in these films is presented; it includes an electron transfer from In₂O₃ to SnO₂, which forms positively charged In₂O₃ nanocrystals that contact the negatively charged SnO₂ nanocrystals. In the presence of In₂O₃ nanocrystals, the activation energy of the electron transfer between SnO₂ nanocrystals decreased substantially because of a decrease in the barrier of electron transfer between SnO₂ crystals under the action of the negative charge. As a result, a percolation cluster of charged SnO₂ crystals formed. At high contents of In₂O₃ (over 20 wt %), the conductivity increased dramatically. The curve of the temperature dependence of conductivity changed because of the appearance of a percolation cluster of In₂O₃ nanocrystals, in which the current passed. The conductivity of a mixed film of this kind differed from that of the nanocrystalline film of pure In₂O₃.     

Gold catalysts supported on ZnO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> for low-temperature CO oxidation

Gold catalysts with loadings ranging from 0.5 to 7.0 wt% on a ZnO/Al₂O₃ support were prepared by the deposition–precipitation method (Au/ZnO/Al₂O₃) with ammonium bicarbonate as the precipitation agent and were evaluated for performance in CO oxidation. These catalysts were characterized by inductively coupled plasma-atom emission spectrometry, temperature programmed reduction, and scanning transmission electron microscopy. The catalytic activity for CO oxidation was measured using a flow reactor under atmospheric pressure. Catalytic activity was found to be strongly dependent on the reduction property of oxygen adsorbed on the gold surface, which related to gold particle size. Higher catalytic activity was found when the gold particles had an average diameter of 3–5 nm; in this range, gold catalysts were more active than the Pt/ZnO/Al₂O₃ catalyst in CO oxidation. Au/ZnO/Al₂O₃ catalyst with small amount of ZnO is more active than Au/Al₂O₃ catalyst due to higher dispersion of gold particles.     

Chemical transformation of cluster osmium thioselenochloride Os<Subscript>3</Subscript>S<Subscript>7</Subscript>SeCl<Subscript>8</Subscript>

The binuclear osmium complex Os₃S₇SeCl₈ was prepared by the reaction of cluster chalcogen chloride K₆Os₂S₂O₆(CN)₈ with an aqueous KCN solution. In the complex, the distance between the osmium atoms is 2.85 Å, and they are linked by μ-SO ₂ ^2? bridges with the OsSOs angle of 75.9°. The osmium coordination number is 6. In the reaction with CN^? ligands under study, the individual fragments of the structure are retained; however, the trinuclear cluster skeleton of Os₃S₇SeCl₈ is destroyed.     

Catalytic peroxide oxidation: The structure of key intermediates in the V<Superscript>V</Superscript>/H<Subscript>2</Subscript>O<Subscript>2</Subscript> system according to quantum chemical data

The inner-sphere isomerization of the peroxo complexes of vanadium(V) with the general formula [VO₆]^? was studied using approximations based on the density functional theory (B3LYP/6-31G**) and the Møller-Plesset perturbation theory (MP2/6-31G**). It was found that the complex [V(=O)(ηO₂)(O₃)]^? containing the O₃ group as a bidentate ligand was the most stable isomer. The transition state region of a rear-rangement of the triperoxo complex [V(ηO₂)₃]^? into [V(=O)(ηO₂)(O₃)]^? was localized. It was found that the activation barrier (～30 kcal/mol) was mainly due to O-O bond cleavage in the peroxo ligand. According to calculations, the reaction proceeds through two intermediate complexes whose structure can be interpreted as that containing coordinated singlet dioxygen (especially in the limiting case) because of noticeably shortened O-O bonds in the ηO₂ ligand. The calculated reaction scheme of the conversion of [V(ηO₂)₃]^? into [V(=O)(ηO₂)(O₃)]^? is qualitatively consistent with the previously found kinetics of the formation of ozone and the oxidation of alkanes, olefins, arenes, and singlet dioxygen traps.