J. Phys. Chem. A 125, 10392−10400 (2021)

Cyclotrimerization of Acetylene on Clusters Co_n⁺/Fe_n⁺/Ni_n⁺(n = 1–16)

Wen Gan¹, Lijun Geng¹, Baoqi Yin¹, Hanyu Zhang¹, Zhixun Luo^1,*, and Klavs Hansen²

1 Beijing National Laboratory for Molecular Science, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;  University of Chinese Academy of Sciences, Beijing 100049, China

2 Center for Joint Quantum Studies and Department of Physics, School of Science, Tianjin University, 92 Weijin Road, Tianjin 300072, China

*  zxluo@iccas.ac.cn

Abstract

Cyclotrimerization of acetylene to benzene has attracted significant interest, but the role of geometric and electronic effects on catalytic chemistry remains unclear. To fully elucidate the mechanism of catalytic acetylene-to-benzene conversion, we have performed a gas-phase reaction study of the Fe_n⁺, Co_n⁺, and Ni_n⁺ (n = 1–16) clusters with acetylene utilizing a customized mass spectrometer. It is found that their reactions with acetylene are initiated by C₂H₂ molecular adsorption and allow for dominant dehydrogenation with the relatively low partial pressure of the acetylene gas. However, at high acetylene concentrations, the cyclotrimerization in M_n⁺ + 3C₂H₂ (M = Fe, Co, Ni) becomes the dominant reaction channel. We demonstrate theoretically the favorable thermodynamics and reaction dynamics leading to the formation of the M⁺(C₆H₆) products. The results are discussed in terms of a cluster-catalyzed multimolecule synergistic effect and the cation−π interactions.