Cracking and Dehydrogenation of Cyclohexane by [(phen)M(X)]+ (M = Ni, Pd, Pt; X = H, CH3) in the Gas Phase

Gas-phase cationic ternary complexes of group 10 metals of the formula [(phen)M(X)](+), where phen = 1,10-phenanthroline (M = Ni, Pd, or Pt; and X = H or CH3), react with cyclohexane via C-H activation, forming the respective cyclohexyl species [(phen)M(c-C6H11)](+). Upon collisional activation, these species undergo two key competing processes: (i) ring opening followed by cracking of the hydrocarbon chain leading to extrusion of propylene and ethylene as major products among other hydrocarbons; and (ii) dehydrogenation of the cyclohexyl ring leading to the loss of one, two, or three hydrogen molecules, with subsequent loss of cyclohexenes or benzene. The relative prevalence of these two pathways strongly depends on the metal ion, with Pt preferring dehydrogenation over ring opening. The multiple catalytic cycles operating within both pathways are described. Density functional theory (DFT) calculations are used to shed light on mechanistic aspects associated with the experimental results.

Automated summary

Gas-phase cationic ternary complexes of group 10 metals react with cyclohexane via C-H activation, leading to the formation of cyclohexyl species. These species undergo two competing processes: ring opening with hydrocarbon chain cracking, and dehydrogenation of the cyclohexyl ring. The prevalence of these processes is metal ion-dependent, with Pt favoring dehydrogenation over ring opening.