Reaction of FeCH₂⁺+ D₂:  Probing the [FeCH₄]⁺Potential Energy Surface

Abstract

A guided-ion beam mass spectrometer is used to study the reactions FeCH 2 + + D 2 and Fe + ( 6 D, 4 F) + CD 4 , thereby experimentally probing the [FeCH 4 ] + potential energy surface (PES). The results obtained are compared to recent theoretical results. Experiment and theory agree that dehydrogenation of methane by Fe + is hindered by a tight, four-center transition state complex. The major discrepancy observed between experiment and theory is in the height of this barrier, which theory predicts to be 75 kJ/mol (92 kJ/mol after correction for zero-point energies) versus our experimental result of 41 ( 6 kJ/mol. Our results can be interpreted by using phase space theory to help understand how various features on the PES control branching ratios among the various channels observed, including extensive hydrogen scrambling in the FeCH 2 + + D 2 reaction. Lastly, results for the [FeCH 4 ] + PES are compared to those for the [CoCH 4 ] + PES obtained in a previous study in order to help assess the effect of potential energy surfaces of different spin in the former case.

The most reactive third-row transition metal: Guided ion beam and theoretical studies of the activation of methane by Ir+

“…If the acceptor orbital is occupied, a repulsive interaction can result leading to inefficient reaction either by more direct abstraction pathways or by introduction of a barrier to the reaction. In our previous studies [9][10][11][12][13][14][15][16], the activation of methane by atomic metal ions was explained by this simple donor-acceptor model, which leads to an oxidative addition mechanism [4]. In such a mechanism, oxidative addition of a C-H bond to M + forms a H-M + -CH 3 intermediate.…”

“…Formation of IrD 2 + has the highest threshold of all processes observed, which is consistent with formation of the high-energy CD 2 neutral. The formation of MD 2 + product ions is unusual and has not been detected for reaction of methane with first-row [8][9][10][12][13][14][15]18], second-row [7,11,[16][17][18], and several thirdrow (La + , W + , Re + , Lu + ) transition metal ions [18,20,21]. However, this product has been observed in reactions of methane with Pt + [19].…”

“…Such ion beam studies also provide insight into the electronic requirements for the activation of methane by transition metal ions and periodic trends in this reactivity. We have applied this methodology to all the first-row and second-row transition metals except Tc [3,[7][8][9][10][11][12][13][14][15][16][17][18] and more recently to several of the third-row metals as well [18][19][20][21]. A significant advantage of these comprehensive studies is the comparison of bond energies and reactivities of all transition-metal complexes, thereby establishing periodic trends.…”

An experimental study of the mechanism for the combined CO and CH bond activation of dimethylether by bare Fe+ ions

“…The energy of the product complex 4 can be estimated to lie ca. 1.9 eV below the entrance channel using a simple additivity approach, i.e., assuming BDE((CH 2 O)Fe + -CH 4 ) ≈ BDE(Fe + -CH 4 ) = 0.59 ± 0.03 eV [33]. For the intermediates 2 and 3 as well as the associated transition structures TS 1/2, TS 1/3, TS 2/4, and TS 3/4, however, no quantitative conclusions can be drawn from experiment alone.…”

A Comprehensive Theoretical Study on the Reactions of Sc+ with CnH2n+2 (n=1–3): Structure, Mechanism, and Potential‐Energy Surface

“…Therefore, we believe that errors resulting from relativistic effects are much less than those due to incomplete basis sets and can be safely neglected. [51] and Co , [52] including detailed reaction mechanisms and PESs, were reported by Armentrout et al [11,12] They identified the four-centered TS shown in Scheme 1 (top). More recently, they also studied the reaction mechanism of Sc with CH 4 by using the CASSCF and MR-SDCI-CASSCF methods.…”