Gas‐Phase Reactions of Cationic Vanadium‐Phosphorus Oxide Clusters with C₂H_x (x=4, 6): A DFT‐Based Analysis of Reactivity Patterns

Abstract

The reactivities of the adamantane-like heteronuclear vanadium-phosphorus oxygen cluster ions [VxP4−xO10].+ (x=0, 2–4) towards hydrocarbons strongly depend on the V/P ratio of the clusters. Possible mechanisms for the gas-phase reactions of these heteronuclear cations with ethene and ethane have been elucidated by means of DFT-based calculations; homolytic C–H bond activation constitutes the initial step, and for all systems the P–O. unit of the clusters serves as the reactive site. More complex oxidation processes, such as oxygen-atom transfer to, or oxidative dehydrogenation of the hydrocarbons require the presence of a vanadium atom to provide the electronic prerequisites which are necessary to bring about the 2e− reduction of the cationic clusters.

Doping Effects in Cluster‐Mediated Bond Activation

“…TheODH process is completed by yet another hydrogen-atom migration from the terminal CH 2 unit to the adjacent V=Os ite,t hus generating 20,f rom which C 2 H 2 can be liberated. [81] For [V 4 O 10 ]C + ,O AT is kinetically and thermodynamically clearly favored;the same holds true for the HATpathway in the case of [P 4 O 10 ]C + .The branching ratio of OATversus HAT/ODH is mainly determined by the relative energies of the barriers TS 13/14 versus TS 13/16 in Figure 15, respectively.F or example,t he OATt ransition structure TS 13/14 is energetically lowest for the [V 4 O 10 ]C + /C 2 H 4 couple and increases upon Figure 14. [100] Ther eactivity patterns observed in the reactions of the well-studied homonuclear clusters [V 4 O 10 ]C + and [P 4 O 10 ]C + with C 2 H 4 are consistent with the calculated PESs.…”

“…[97] With regard to heteronuclear clusters, for example,[ V 4Àn P n O 10 ]C + , [80] [(V 2 O 5 ) n (SiO 2 ) m ] +/À (n = 1, 2; m = 1-4), [98] or [V n Al m O o ] +/À (n + m = 2, 3, 4; o = 3-10), [99] they all possess ah igh spin density located at at erminal oxygen atom that is not bound to the transition metal vanadium but to the main-group atom, that is AlÀO t C,S i À O t C,o rP ÀO t C.T he V=O t unit is completely inert. [68,96] However,a s shown in Table 1, an entirely different scenario is encountered when these cluster ions react with C 2 H x (x = 4, 6), [81,[100][101][102] and the major questions raised by the unexpected branching ratios can be summarized as follows: 1) What are the reasonable reaction mechanisms for these VPO clusters when subjected to these substrates? Common to the thermal reactions of all [V n P 4Àn O 10 ]C + clusters with CH 4 is af acile scission of the CÀHb ond with efficiencies of more than 60 %r elative to the collision rate.…”

“…[3,16,28] Explanations and insight were sought by DFT studies, [81] and here Iwill only describe part of the results obtained for the [V 2 P 2 O 10 ]C + /C 2 H 4 couple. [3,16,28] Explanations and insight were sought by DFT studies, [81] and here Iwill only describe part of the results obtained for the [V 2 P 2 O 10 ]C + /C 2 H 4 couple.…”

Generation of free hydrogen atoms in thermal reaction of ethane with AuNbO 3 + cluster cations

“…The exiting channels of these reactions were mainly hydrogen (H 2 ) elimination [50][51][52], ethylene elimination [32,50,51,[53][54][55][56][57][58], hydrogen-atom abstraction (HAA) [51,53,57,[59][60][61][62], oxygen-atom transfer (OAT) [50,53,55,56], and acetaldehyde formation [50,53]. Only the reaction with CrO 2 + [50] was reported to generate the free H atom, to the best of our knowledge.…”

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

“…[128][129][130][131][132][133][134][135] Zheng et al reported the photoelectron spectroscopy of MAlO x and M x AlO 2 -(M = Ti or V; x = 1, 2, or 3) BONCs. 65,125 Studies of BONC ions are becom-ing increasingly widespread: e.g., AuNbO 3 [138][139][140] and AlYO 3 + . 89,141 All the above systems are charged BONCs.…”