Gas-Phase Reaction Studies of Dipositive Hafnium and Hafnium Oxide Ions: Generation of the Peroxide HfO₂²⁺

Abstract

Fourier transform ion cyclotron resonance mass spectrometry was used to characterize the gas-phase reactivity of Hf dipositive ions, Hf(2+)and HfO(2+), toward several oxidants: thermodynamically facile O-atom donor N(2)O, ineffective donor CO, and intermediate donors O(2), CO(2), NO, and CH(2)O. The Hf(2+) ion exhibited electron transfer with N(2)O, O(2), NO, and CH(2)O, reflecting the high ionization energy of Hf(+). The HfO(2+) ion was produced by O-atom transfer to Hf(2+) from N(2)O, O(2), and CO(2), and the HfO(2)(2+) ion by O-atom transfer to HfO(2+) from N(2)O; these reactions were fairly efficient. Density functional theory revealed the structure of HfO(2)(2+) as a peroxide. The HfO(2)(2+) ion reacted by electron transfer with N(2)O, CO(2), and CO to give HfO(2)(+). Estimates were made for the second ionization energies of Hf (14.5 ± 0.5 eV), HfO (14.3 ± 0.5 eV), and HfO(2) (16.2 ± 0.5 eV), and also for the bond dissociation energies, D[Hf(2+)-O] = 686 ± 69 kJ mol(-1) and D[OHf(2+)-O] = 186 ± 98 kJ mol(-1). The computed bond dissociation energies, 751 and 270 kJ mol(-1), respectively, are within these experimental ranges. Additionally, it was found that HfO(2)(2+) oxidized CO to CO(2) and is thus a catalyst in the oxidation of CO by N(2)O and that Hf(2+) activates methane to produce a carbene, HfCH(2)(2+).

Sequential Gas-Phase Activation of Carbon Dioxide and Methane by [Re(CO)2]+: The Sequence of Events Matters!

“…For example, some bare metal cations M + and metal-containing clusters give rise to oxygen-atom transfer (OAT) from CO 2 ; ,− this reaction is driven by the high oxophilicities of these species . In addition to OAT, charge transfer accompanied by coulomb explosion can occur in the thermal reactions of CO 2 with some doubly charged cations, , and a coupled oxygen–sulfur ligand-transfer mechanism is operative in the reactions of CO 2 with diatomic [MS] + (M = Y, Zr, Nb, Sc, Ti), generating COS and MO + . − Further, C–X bond formation is accessible under ambient conditions by the insertion of CO 2 in an Y + –X bond (Y = metal or non-metal atoms; X = H, − C, OH , ). In addition, η 2 -coordinated CO 2 on [MgOH] + undergoes C–C coupling with CH 3 Cl to produce an acetyl unit .…”

Unveiling the Zirconium and Hafnium Speciation in Fluoride‐Nitric Acid Solutions by Paper Spray Ionization Mass Spectrometry Combined with DFT Calculations

“…The formation of positively charged, highly energetic species such as HfO 2+ , was determined in a study by mass spectrometry using FTICR‐MS (Fourier‐transform ion cyclotron resonance mass spectrometry), combined with computational calculations at DFT−B3LYP/LANL2TZ(f) level [29] . The formation of the dimeric species (H 3 O) 3 [Hf 2 F 7 (NO 3 ) 2 (H 2 O) 2 ] ⋅ 4H 2 O 2+ , from the oxophilic monomer [HfO(H 2 O) 4 ] 2+ provided high thermodynamic stability, c.a .…”

“…The formation of positively charged, highly energetic species such as HfO 2 + , was determined in a study by mass spectrometry using FTICR-MS (Fourier-transform ion cyclotron resonance mass spectrometry), combined with computational calculations at DFTÀ B3LYP/LANL2TZ(f) level. [29] The formation of the dimeric species (H 3 O) 3 [30] and the resistance of the superhalogen anion [HfF 5 ] À to reactions with O 2 . [31] The (H 3 O) 2 [21] and HfF 4 • 3H 2 O.…”

Hafnia–Silica Cryogels: Solvent‐Assisted Textural and Catalytic Control in the Citronellal Cyclization

“…[3] Pure hafnia was also evaluated in the H 2 O 2 decomposition, [4] and gas-phase studies recently demonstrated the potential of hafnium oxide cations in oxidation reactions. [5] We are not aware of any further direct catalytic application of hafnium oxide, and none of them refers to catalytic CÀC bond forming processes such as the carbonylene reaction.…”