Cyclotrimerization of Acetylene on Clusters Con+/Fen+/Nin+(n=1-16)

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(+) + 3C(2)H(2) (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-pi interactions.

Automated summary

The study investigates the reaction mechanisms of Fe-n(+), Co-n(+), and Ni-n(+) clusters with acetylene in the gas phase, revealing predominant dehydrogenation at low acetylene partial pressures and cyclotrimerization at high acetylene concentrations. The favorable thermodynamics and reaction dynamics leading to the formation of M+ (C6H6) products are theoretically demonstrated, with discussions on cluster-catalyzed multimolecule synergistic effects and cation-pi interactions.