Oxide Cluster Anions Research Articles

Thermal methane activation by La(6)O(10)(-) cluster anions.

The first example of a metal oxide cluster anion, La6 O10 (-) that can activate methane under ambient conditions is reported. This reaction is facilitated by the oxygen-centered radical (O(-⋅) ) and follows the hydrogen atom transfer mechanism. The La6 O10 (-) has a high vertical electron detachment energy (VDE=4.06 eV) and a high symmetry (C4v ).

RH and H2 Production in Reactions between ROH and Small Molybdenum Oxide Cluster Anions

To test recent computational studies on the mechanism of metal oxide cluster anion reactions with water [Ramabhadran, R. O.; et al. J. Phys. Chem. Lett. 2010, 1, 3066; Ramabhadran, R. O.; et al. J. Am. Chem. Soc. 2013, 135, 17039], the reactivity of molybdenum oxo–cluster anions, Mo(x)O(y)(–) (x = 1 – 4; y ≤ 3x) toward both methanol (MeOH) and ethanol (EtOH) has been studied using mass spectrometric analysis of products formed in a high-pressure, fast-flow reactor. The size-dependent product distributions are compared to previous Mo(x)O(y)(–) + H2O/D2O reactivity studies, with particular emphasis on the Mo2O(y)(–) and Mo3O(y)(–) series. In general, sequential oxidation, Mo(x)O(y)(–) + ROH → Mo(x)O(y+1)(–) + RH, and addition reactions, Mo(x)O(y)(–) + ROH → Mo(x)O(y+1)RH(–), largely corresponded with previously studied Mo(x)O(y)(–) + H2O/D2O reactions [Rothgeb, D. W., Mann, J. E., and Jarrold, C. C. J. Chem. Phys. 2010, 133, 054305], though with much lower rate constants than those determined for Mo(x)O(y)(–) + H2O/D2O reactions. This finding is consistent with the computational studies that suggested that −H mobility on the cluster–water complex was an important feature in the overall reactivity. There were several notable differences between cluster–ROH and cluster–water reactions associated with lower R–OH bond dissociation energies relative to the HO–H dissociation energy.

CO Oxidation Promoted by Gold Atoms Supported on Titanium Oxide Cluster Anions

Laser ablation generated Au(x)(TiO2)(y)O(z)(-) (x = 0, 1; y = 2, 3; z = 1, 2) oxide cluster anions have been mass-selected using a quadrupole mass filter and reacted with CO in a hexapole collision cell. The reactions have been characterized by time-of-flight mass spectrometry and density functional theory calculations. Gold-titanium bimetallic oxide clusters Au(TiO2)(y)O(z)(-) are more reactive in CO oxidation than pure titanium oxide clusters (TiO2)(y)O(z)(-). The computational studies identify the dual roles that the gold atom plays in CO oxidation: functioning as a CO trapper and electron acceptor. Both factors are important for the high reactivity of Au(TiO2)(y)O(z)(-) clusters. To the best of our knowledge, this is the first example of CO oxidation by gold-containing heteronuclear oxide clusters, which provides molecular-level insights into the roles of gold in CO oxidation over oxide supports.

Consecutive Oxygen-for-Sulfur Exchange Reactions between Vanadium Oxide Cluster Anions and Hydrogen Sulfide

Vanadium oxide cluster anions Vm(16)On(-) and Vm(18)On(-) were prepared by laser ablation and reacted with hydrogen sulfide (H2S) in a fast flow reactor under thermal collision conditions. A time-of-flight mass spectrometer was used to detect the cluster distributions before and after the interactions with H2S. The experiments suggest that the oxygen-for-sulfur (O/S) exchange reaction to release water was evidenced in the reactor for most of the cluster anions: VmOn(-) + H2S → VmOn-1S(-) + H2O. For reactions of clusters VO3(-) and VO4(-) with H2S, consecutive O/S exchange reactions led to the generation of sulfur containing vanadium oxide cluster anions VO3-kSk(-) (k = 1-3) and VO4-kSk(-) (k = 1-4). Density functional theory calculations were performed for the reactions of VO3-4(-) with H2S, and the results indicate that the O/S exchange reactions are both thermodynamically and kinetically favorable, which supports the experimental observations. The reactions of VmOn(+) cluster cations with H2S have been reported previously (Jia, M.-Y.; Xu, B.; Ding, X.-L.; Zhao, Y.-X.; He, S.-G.; Ge, M.-F. J. Phys. Chem. C 2012, 116, 9043), and this study of cluster anions provides further new insights into the transformations of H2S over vanadium oxides at the molecular level.

Reactivity of Oxygen Radical Anions Bound to Scandia Nanoparticles in the Gas Phase: CH Bond Activation

The activation of C-H bonds in alkanes is currently a hot research topic in chemistry. The atomic oxygen radical anion (O(-·)) is an important species in C-H activation. The mechanistic details of C-H activation by O(-·) radicals can be well understood by studying the reactions between O(-·) containing transition metal oxide clusters and alkanes. Here the reactivity of scandium oxide cluster anions toward n-butane was studied by using a high-resolution time-of-flight mass spectrometer coupled with a fast flow reactor. Hydrogen atom abstraction (HAA) from n-butane by (Sc2O3)(N)O(-) (N=1-18) clusters was observed. The reactivity of (Sc2O3)(N)O(-) (N=1-18) clusters is significantly sizedependent and the highest reactivity was observed for N=4 (Sc8O13(-)) and 12 (Sc24O37(-)). Larger (Sc2O3)(N)O(-) clusters generally have higher reactivity than the smaller ones. Density functional theory calculations were performed to interpret the reactivity of (Sc2O3)(N)O(-) (N=1-5) clusters, which were found to contain the O(-·) radicals as the active sites. The local charge environment around the O(-·) radicals was demonstrated to control the experimentally observed size-dependent reactivity. This work is among the first to report HAA reactivity of cluster anions with dimensions up to nanosize toward alkane molecules. The anionic O(-·) containing scandium oxide clusters are found to be more reactive than the corresponding cationic ones in the C-H bond activation.

Generation and reactivity of putative support systems, Ce-Al neutral binary oxide nanoclusters: CO oxidation and C–H bond activation

Both ceria (CeO2) and alumina (Al2O3) are very important catalyst support materials. Neutral binary oxide nanoclusters (NBONCs), CexAlyOz, are generated and detected in the gas phase and their reactivity with carbon monoxide (CO) and butane (C4H10) is studied. The very active species CeAlO4 (●) can react with CO and butane via O atom transfer (OAT) and H atom transfer (HAT), respectively. Other CexAlyOz NBONCs do not show reactivities toward CO and C4H10. The structures, as well as the reactivities, of CexAlyOz NBONCs are studied theoretically employing density functional theory (DFT) calculations. The ground state CeAlO4 (●) NBONC possesses a kite-shaped structure with an OtCeObObAlOt configuration (Ot, terminal oxygen; Ob, bridging oxygen). An unpaired electron is localized on the Ot atom of the AlOt moiety rather than the CeOt moiety: this Ot centered radical moiety plays a very important role for the reactivity of the CeAlO4 (●) NBONC. The reactivities of Ce2O4, CeAlO4 (●), and Al2O4 toward CO are compared, emphasizing the importance of a spin-localized terminal oxygen for these reactions. Intramolecular charge distributions do not appear to play a role in the reactivities of these neutral clusters, but could be important for charged isoelectronic BONCs. DFT studies show that the reaction of CeAlO4 (●) with C4H10 to form the CeAlO4H●C4H9 (●) encounter complex is barrierless. While HAT processes have been previously characterized for cationic and anionic oxide clusters, the reported study is the first observation of a HAT process supported by a ground state neutral oxide cluster. Mechanisms for catalytic oxidation of CO over surfaces of AlxOy∕MmOn or MmOn∕AlxOy materials are proposed consistent with the presented experimental and theoretical results.

Experimental and Theoretical Study of the Reactions between MO2– (M = Fe, Co, Ni, Cu, and Zn) Cluster Anions and Hydrogen Sulfide

Transition metal oxide cluster anions M(m)(18)O(n)(-) (M = Fe, Co, Ni, Cu, and Zn) were prepared by laser ablation and reacted with H2S in a fast flow reactor under thermal collision conditions. A time-of-flight mass spectrometer was used to detect the cluster distributions before and after the interactions with H2S. The experiments reveal a suite of oxygen/sulfur (O/S) exchange and oxygen/sulfydryl (O/SH) exchange reactions. The O/S exchange reaction to release water was evidenced for all of the MO2(-) cluster anions: MO2(-) + H2S → MOS(-) + H2O, whereas the O/SH exchange reaction to derive MOSH(-) and OH species was only observed for reactions of NiO2(-), CuO2(-), and ZnO2(-). Density functional theory calculations were performed for reaction mechanisms of MO2(-) + H2S (M = Fe, Co, Ni, Cu, and Zn). The computational results are generally in good agreement with the experimental results. This gas-phase study provides an insight into the metal dependent reactivity in the removal of H2S over metal oxides.

Gas-Phase Synthesis of Singly and Multiply Charged Polyoxovanadate Anions Employing Electrospray Ionization and Collision Induced Dissociation

Electrospray ionization mass spectrometry (ESI-MS) combined with in-source fragmentation and tandem mass spectrometry (MS/MS) experiments were used to generate a wide range of singly and multiply charged vanadium oxide cluster anions including VxOy(n-) and VxOyCl(n-) ions (x = 1-14, y = 2-36, n = 1-3), protonated clusters, and ligand-bound polyoxovanadate anions. The cluster anions were produced by electrospraying a solution of tetradecavanadate, V14O36Cl(L)5 (L = Et4N(+), tetraethylammonium), in acetonitrile. Under mild source conditions, ESI-MS generates a distribution of doubly and triply charged VxOyCl(n-) and VxOyCl(L)((n-1)-) clusters predominantly containing 14 vanadium atoms as well as their protonated analogs. Accurate mass measurement using a high-resolution LTQ/Orbitrap mass spectrometer (m/Δm = 60,000 at m/z 410) enabled unambiguous assignment of the elemental composition of the majority of peaks in the ESI-MS spectrum. In addition, high-sensitivity mass spectrometry allowed the charge state of the cluster ions to be assigned based on the separation of the major from the much less abundant minor isotope of vanadium. In-source fragmentation resulted in facile formation of smaller VxOyCl((1-2)-) and VxOy ((1-2)-) anions. Collision-induced dissociation (CID) experiments enabled systematic study of the gas-phase fragmentation pathways of the cluster anions originating from solution and from in-source CID. Surprisingly simple fragmentation patterns were obtained for all singly and doubly charged VxOyCl and VxOy species generated through multiple MS/MS experiments. In contrast, cluster anions originating directly from solution produced comparatively complex CID spectra. These results are consistent with the formation of more stable structures of VxOyCl and VxOy anions through low-energy CID. Furthermore, our results demonstrate that solution-phase synthesis of one precursor cluster anion combined with gas-phase CID is an efficient approach for the top-down synthesis of a wide range of singly and multiply charged gas-phase metal oxide cluster anions for subsequent investigations of structure and reactivity using mass spectrometry and ion spectroscopy techniques.

Asymmetric Partitioning of Metals among Cluster Anions and Cations Generated via Laser Ablation of Mixed Aluminum/Group 6 Transition Metal Targets

While high-power laser ablation of metal alloys indiscriminately produces gas-phase atomic ions in proportion to the abundance of the various metals in the alloy, gas-phase ions produced by moderate-power laser ablation sources coupled with molecular beams are formed by more complicated mechanisms. A mass spectrometric study that directly compares the mass distributions of cluster anions and cations generated from laser ablation of pure aluminum, an aluminum/molybdenum mixed target, and an aluminum/tungsten mixed target is detailed. Mass spectra of anionic species generated from the mixed targets showed that both tungsten and molybdenum were in higher abundance in the negatively charged species than in the target material. Mass spectra of the cationic species showed primarily Al(+) and aluminum oxide and hydroxide cluster cations. No molybdenum- or tungsten-containing cluster cations were definitively assigned. The asymmetric distribution of aluminum and Group 6 transition metals in cation and anion cluster composition is attributed to the low ionization energy of atomic aluminum and aluminum suboxide clusters. In addition, the propensity of both molybdenum and tungsten to form metal oxide cluster anions under the same conditions that favor metallic aluminum cluster anions is attributed to differences in the optical properties of the surface oxide that is present in the metal powders used to prepare the ablation targets. Mechanisms of mixed metal oxide clusters are considered.

Reactivity of Atomic Oxygen Radical Anions Bound to Titania and Zirconia Nanoparticles in the Gas Phase: Low-Temperature Oxidation of Carbon Monoxide

Titanium and zirconium oxide cluster anions with dimensions up to nanosize are prepared by laser ablation and reacted with carbon monoxide in a fast low reactor. The cluster reactions are characterized by time-of-flight mass spectrometry and density functional theory calculations. The oxygen atom transfers from (TiO(2))(n)O(-) (n = 3-25) to CO and formations of (TiO(2))(n)(-) are observed, whereas the reactions of (ZrO(2))(n)O(-) (n = 3-25) with CO generate the CO addition products (ZrO(2))(n)OCO(-), which lose CO(2) upon the collisions (studied for n = 3-9) with a crossed helium beam. The computational study indicates that the (MO(2))(n)O(-) (M = Ti, Zr; n = 3-8) clusters are atomic radical anion (O(-)) bonded systems, and the energetics for CO oxidation by the O(-) radicals to form CO(2) is strongly dependent on the metals as well as the cluster size for the titanium system. Atomic oxygen radical anions are important reactive intermediates, while it is difficult to capture and characterize them for condensed phase systems. The reactivity pattern of the O(-)-bonded (TiO(2))(n)O(-) and (ZrO(2))(n)O(-) correlates very well with different behaviors of titania and zirconia supports in the low-temperature catalytic CO oxidation.

Hydrothermal Syntheses, Crystal Structures, and Thermal Gravimetric Analysis (TGA) of Two Inorganic-Organic Hybrid Materials: [bphx][Mo6O19] and [bphx]3[H2W12O40]·3H2O

Two novel organic-inorganic hybrid polyoxometalate supra molecular compounds have been prepared through hydrothermal synthesis methods, namely [bphx][Mo6O19] (1) and [bphx]3[H2W12O40]·3H2O (2) [bphx = 1,6-bis(pyridinium)hexane], and characterized by single-crystal X-ray diffraction, IR spectroscopy, and thermal gravimetric analysis (TGA). The results indicate that these compounds are composed of isolated organic cation and inorganic anion by electrostatic interaction. The molybdenum oxide cluster [Mo6O19]2− anion in compound 1 is Lindqvist structure, and the tungsten oxide cluster anion in compound 2 is the classical Keggin-type. Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.

C–H bond activation by aluminum oxide cluster anions, an experimental and theoretical study

Aluminum oxide cluster anions are produced by laser ablation and reacted with n-butane in a fast flow reactor. A reflectron time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Aluminum oxide clusters Al₂O4,6⁻ and Al₃O₇⁻ can react with n-C₄H₁₀ to produce Al₂O4,6H⁻ and Al₃O₇⁻, respectively, while cluster Al₃O₆⁻ reacts with n-C₄H₁₀ to produce both the Al₃O₆H⁻ and Al₃O₆H₂⁻. The theoretical calculations are performed to study the structures and bonding properties of clusters Al₂O4,6⁻ and Al₃O6,7⁻ as well as the reaction mechanism of Al₂O₄⁻ + n-C₄H₁₀. The calculated results show that the mononuclear oxygen-centred radicals (O⁻˙) on Al₂O4,6⁻ and Al₃O₇⁻, and oxygen-centred biradical on Al₃O₆⁻ are the active sites responsible for the observed hydrogen atom abstraction reactivity. Furthermore, mechanism investigation of the O⁻˙ generation in Al₃O₇⁻ upon O₂ molecule adsorption on un-reactive Al₃O₅⁻ is performed by theoretical calculations.

Experimental and Theoretical Study of the Reactions between Manganese Oxide Cluster Anions and Hydrogen Sulfide

Experimental and Theoretical Study of the Reactions between Manganese Oxide Cluster Anions and Hydrogen Sulfide

Reactions of Sc2O4− and La2O4− Clusters with CO: A comparative study

Scandium and lanthanum oxide cluster anions Sc2O4− and La2O4− are prepared by laser ablation and reacted with CO in a fast flow reactor. A time of flight mass spectrometer is used to detect the cluster distribution before and after the reactions. In the reaction of Sc2O4− with CO, Sc2O3− anion is observed as a product. In sharp contrast, no product anion is observed for La2O4−+CO although the CO reactant gas causes a fast depletion of La2O4−. The experiment thus provides evidence of electron auto-detachment in the reaction of La2O4− with CO. Density functional theory calculations are performed to study the mechanisms for the above two reactions and the results well interpret the experimental observations. This study is among the first to report electron auto-detachment in the oxidation of CO by metal oxide cluster anions.

Interaction of vanadium oxide cluster anions with water: an experimental and theoretical study on reactivity and mechanism

Vanadium oxide cluster anions (V(x)O(y)(-), x = 2-3; y = 3-7) are produced by laser ablation and reacted with water in a fast flow reactor. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Reaction channels of molecular hydrogen elimination (for V(2,3)O(3)(-)), water association (for V(2)O(5)(-) and V(3)O(6,7)(-)) and the coexistence of both channels (for V(2)O(4)(-) and V(3)O(4,5)(-)) are observed. V(2)O(6)(-) and V(3)O(8)(-) are nearly inert toward water. Density functional theory (DFT) calculations are performed to study the reaction mechanism of V(2)O(3)(-) in different spin states with water and the results support the experimental observation. The reaction mechanism of V(2)O(3)(+) with water is also studied, which is in agreement with the experimental report in previous literature [Eur. J. Inorg. Chem., 2008, 4961] that molecular hydrogen elimination is a minor reaction channel for V(2)O(3)(+) + H(2)O. The influence of cluster charge states and oxidation states of vanadium atoms on the cluster reactivity are presented based on the experimental and theoretical studies.

Kinetic study of the reaction of vanadium and vanadium–titanium oxide cluster anions with SO2

The reactivity of mass-selected V(4)O(10)(-) cluster anions towards sulphur dioxide is investigated in an ion trap under multi-collision conditions. Gas phase reaction kinetics are studied as a function of temperature (T(R) = 150-275 K). The binding energy of SO(2) to V(4)O(10)(-) is obtained by analyzing the experimental low pressure rate constants, employing the Lindemann energy transfer model for association reactions in conjunction with statistical RRKM theory. In addition, infrared multiple photon dissociation spectroscopy is used in conjunction with density functional theory for the structural assignment of the [V(4)O(10)(-), SO(2)] complex, revealing a square pyramidal structure with the SO(2) molecule incorporated in the vanadium oxide framework. Energy profiles are calculated for the reaction between V(4)O(10)(-) and V(6)O(15)(-) with SO(2). Whereas the transition structures along the reaction pathway of V(4)O(10)(-) with SO(2) have energies below those of the separated partners, the reaction of V(6)O(15)(-) with SO(2) proceeds via a transition structure with energy higher than the educts. The role of cluster size and composition is investigated by studying the reaction kinetics of larger (V(6)O(15)(-) and V(8)O(20)(-)) and titanium doped (V(3)TiO(10)(-) and V(2)Ti(2)O(10)(-)) vanadium oxide clusters with SO(2). The observed cluster size and composition dependencies are discussed.

Experimental and Theoretical Study of Hydrogen Atom Abstraction fromn-Butane by Lanthanum Oxide Cluster Anions

Lanthanum oxide cluster anions are prepared by laser ablation and reacted with n-C(4)H(10) in a fast flow reactor. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. (La(2)O(3))(m=1-3)OH(-) and La(3)O(7)H(-) are observed as products, which suggests the occurrence of hydrogen atom abstraction reactions: (La(2)O(3))(m=1-3)O(-) + n-C(4)H(10) → (La(2)O(3))(m=1-3)OH(-) + C(4)H(9) and La(3)O(7)(-) + n-C(4)H(10) → La(3)O(7)H(-) + C(4)H(9). Density functional theory (DFT) calculations are performed to study the structures and bonding properties of La(2)O(4)(-), La(3)O(7)(-), and La(4)O(7)(-) clusters. The calculated results show that each of La(2)O(4)(-) and La(4)O(7)(-) contains one oxygen-centered radical (O(-•)) which is responsible for the high reactivity toward n-C(4)H(10). La(3)O(7)(-) contains one oxygen-centered radical (O(-•)) and one superoxide unit (O(2)(-•)), and the O(-•) is responsible for its high reactivity toward n-C(4)H(10). The O(-•) and O(2)(-•) can be considered to be generated by the adsorption of an O(2) molecule onto the singlet La(3)O(5)(-) with electron transfer from a terminally bonded oxygen ion (O(2-)) to the O(2). This may help us understand the mechanism of the formation of O(-•) and O(2)(-•) radicals in lanthanum oxide systems. The reaction mechanisms of La(2)O(4)(-) + n-C(4)H(10) and La(3)O(7)(-) + n-C(4)H(10) are also studied by the DFT calculations, and the calculated results are in good agreement with the experimental observations.

Experimental and Theoretical Study of the Reactions between Cerium Oxide Cluster Anions and Carbon Monoxide: Size-Dependent Reactivity of CenO2n+1–(n= 1–21)

Reactions of cerium oxide cluster anions with carbon monoxide are investigated by time-of-flight mass spectrometry and density functional theory computations aided with molecular dynamics simulations. Interesting size-dependent reactivity of the CenO2n+1– cluster series with n = 1–21 is observed: (1) the small n = 1–3 clusters have no or very low reactivity toward CO, (2) the large n = 4–21 clusters can oxidize CO to produce CO2, and (3) the n = 4 (Ce4O9–), 6 (Ce6O13–), 7 (Ce7O15–), and 12 (Ce12O25–) clusters have relatively higher reactivity than their neighboring systems Ce3O7–, Ce5O11–, Ce8O17–, etc. Theoretical study indicates that the CenO2n+1– clusters contain oxygen-centered radicals (O–•) and the nature of the spin density distributions within the clusters controls the experimentally observed size-dependent reactivity. The experiment and theory in this study suggest that the metal oxide clusters as large as Ce21O43– can contain the reactive O–• centers, at which the size may be large enough to mimic related active sites in condensed phase catalysts. Oxidation of CO by O2 at low temperature is of widespread importance and reactive oxygen species including O–• are usually involved. The nature of the O–• radicals is demonstrated to be able to further address the goodness of nanocrystalline CeO2 in the low-termperautre CO oxidation.

Collision-Induced Dissociation and Density Functional Theory Studies of CO Adsorption over Zirconium Oxide Cluster Ions: Oxidative and Nonoxidative Adsorption

Zirconium oxide cluster cations and anions are produced by laser ablation and reacted with CO in a fast flow reactor. The CO adsorption products Zr(x)O(y)CO(+) are observed for most of the generated cationic clusters (Zr(x)O(y)(+) = Zr(2)O(5,6)(+), Zr(3)O(7,8)(+), Zr(4)O(9,10)(+)...) while only specific anionic systems (Zr(x)O(y)(-) = Zr(3)O(7)(-), Zr(4)O(9)(-)...) absorb CO to produce Zr(x)O(y)CO(-). To study how the CO molecule is adsorbed on the clusters, the Zr(x)O(y)CO(±) products are mass-selected by a time-of-flight mass spectrometer (TOF-MS) and collided with a crossed helium beam. The fragment ions from collision-induced dissociation (CID) are detected by a secondary TOF-MS. Loss of CO and CO(2) is observed upon the collision of the helium beam with Zr(x)O(y)CO(+) and Zr(x)O(2x+1)CO(-), respectively. Density functional theory calculations indicate that oxidative and nonoxidative adsorption of CO takes place over Zr(3)O(7)(-) and Zr(3)O(7)(+), respectively. This is consistent with the CID experiments.

CH Activation on Aluminum–Vanadium Bimetallic Oxide Cluster Anions

Aluminum-vanadium bimetallic oxide cluster anions (BMOCAs) have been prepared by laser ablation and reacted with ethane and n-butane in a fast-flow reactor. A time-of-flight mass spectrometer was used to detect the cluster distribution before and after the reactions. The observation of hydrogen-containing products AlVO(5)H(-) and Al(x)V(4-x)O(11-x)H(-) (x=1-3) strongly suggests that AlVO(5)(-) and Al(x)V(4-x)O(11-x)(-) (x=1-3) can react with ethane and n-butane by means of an oxidative dehydrogenation process at room temperature. Density functional theory studies have been carried out to investigate the structural, bonding, electronic, and reactive properties of these BMOCAs. Terminal-oxygen-centered radicals (O(t)(.)) were found in all of the reactive clusters, and the O(t)(.) atoms, which prefer to be bonded with Al rather than V atoms, are the active sites of these clusters. All the hydrogen-abstraction reactions are favorable both thermodynamically and kinetically. To the best of our knowledge, this is the first example of hydrogen-atom abstraction by BMOCAs and may shed light on understanding the mechanisms of C−−H activation on the surface of alumina-supported vanadia catalysts.