Probing the [CoC₂H₆]⁺Potential Energy Surface:  A Detailed Guided-Ion Beam Study

Abstract

The potential energy surface for the CoC2H6 + system is probed by using a guided-ion beam tandem mass spectrometer in conjunction with a dc discharge/flow tube ion source. Bimolecular reactions of Co+ + C2H6, Co+(C2H4) + H2 (D2), and CoCH2 + + CH4 (CD4) are examined, as well as threshold collisional activation of Co+(C2H6) and Co+(C2H4) with Xe. The results allow details of the [CoC2H6]+ potential energy surface (PES) to be elucidated. Key features of the PES include barrier heights of 1.04 ± 0.11 eV (0.29 ± 0.09 eV in excess of the endothermicity) for the reaction of Co+ with ethane to form CoCH2 + + CH4 and of 0.32 ± 0.12 eV for the exothermic reaction to form Co+(C2H4) + H2. From the collisional activation studies, we determine 0 K bond dissociation energies for Co+−C2H4 and Co+−C2H6 complexes of 1.86 ± 0.07 and 1.04 ± 0.05 eV, respectively, in good agreement with literature values. D 0(DCo+−C2H4) = 1.13 ± 0.16 eV is also determined although it is somewhat more speculative.

Probing the [CoC3H8]+Potential Energy Surface: A Detailed Guided-Ion Beam Study

“…27,28 The results presented here extend this work to include the [CoC 3 H 8 ] + PES. Specifically, we reexamine the Co + + C 3 H 8 system with higher sensitivity than previous studies; we study several bimolecular reactions, Co + (C 3 H 6 ) + H 2 (D 2 ), Co + (C 2 H 4 ) + CH 4 (CD 4 ), CoCH 2 + + C 2 H 6 ; and we use threshold collision activation [29][30][31][32] (TCA) to characterize the Co + (C 3 H 8 ) intermediate.…”

“…36 CID of the Co + -(C 3 H 6 ) and Co + (C 2 H 4 ) beams showed products and Co + thresholds consistent with those reported previously. 28,29 Evidence for possible excited states is discussed in more detail below and there is a possibility that the Co + (C 2 H 4 ) beam contains small amounts of CoN 2 + , in analogy with recent studies of FeCO + . 37 Hydrocarbon gases were obtained from Matheson in high purity (>99%) and used without further purification.…”

“…In the reaction of Co + (C 2 H 4 ) + D 2 to form CoC 2 H 4 D + + D, we have shown that the structure is most likely the DCo + (C 2 H 4 ) structure based on isotope scrambling patterns and thermodynamics. 28 The threshold for reaction 34 leads to D 0 [D-Co + (C 2 H 4 )] ) 1.10 ( 0.15 eV, in agreement with that obtained in the D 2 reaction of 1.28 ( 0.13 eV. 28 Alternatively, we can use this threshold to determine D 0 -(DCo + -C 2 H 4 ) ) 0.95 ( 0.18 eV, in agreement with that obtained in the D 2 reaction of 1.13 ( 0.16 eV.…”

“…28 The threshold for reaction 34 leads to D 0 [D-Co + (C 2 H 4 )] ) 1.10 ( 0.15 eV, in agreement with that obtained in the D 2 reaction of 1.28 ( 0.13 eV. 28 Alternatively, we can use this threshold to determine D 0 -(DCo + -C 2 H 4 ) ) 0.95 ( 0.18 eV, in agreement with that obtained in the D 2 reaction of 1.13 ( 0.16 eV. 28 As explained in detail elsewhere, 28 it is consistent that these BDEs are substantially lower than those for Co + -D and Co + -C 2 H 4 ( Table 3) because the Co + -D bond utilizes the 4s orbital on the metal while strong bonding of C 2 H 4 to Co + relies on having an empty 4s orbital.…”

Propane transformations on aluminum chloride—cobalt chloride clusters: a quantum chemical study

“…Similar activation barriers to ox idative addition at the C-C bond in ethane or propane were obtained in guided ion beam mass spectrometry stud ies of reactions of Co + ions. 26, 28 According to our calculations, not only isolated cat ions, but also bimetallic ionic complexes CoAlCl 4 + can activate alkane C-C bonds with moderately high ac tivation barriers. In the case of the bimetallic cluster C 3 H 8 •CoAlCl 4 + , we located the transition state TS3 of oxidative addition of propane at the C-C bond, which lies on the pathway from complex 2d to intermediate IM1.…”