Methane activation by chromium oxide cations in the gas phase: a theoretical study

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Chemical Kinetics

Background:

• Transition metal cations play crucial roles in catalytic processes.
• Understanding the mechanisms of C-H bond activation is vital for developing new chemical transformations.
• Chromium dioxide cation's reactivity with methane presents an interesting case study.

Purpose of the Study:

• To elucidate the potential energy hypersurfaces for C-H bond activation of methane by chromium dioxide cation.
• To investigate the influence of different electronic states (doublet and quartet) on the reaction.
• To compare the reactivity of chromium dioxide cation with chromium monoxide cation.

Main Methods:

• Density Functional Theory (DFT) with B3LYP formulation.
• Characterization of minima and transition states on potential energy hypersurfaces.
• Exploration of reaction pathways using BP86 and B3LYP* functionals, and CCSD(T) approach.
• Investigation of state-selective reactivity.

Main Results:

• Detailed potential energy hypersurfaces for methane C-H bond activation by CrO2+ were mapped.
• Both ground doublet and excited quartet states were analyzed.
• Calculated pathways involve spin inversions, which lower transition state barriers but are not dominant.
• Reactivity of CrO+ with methane was compared to CrO2+.

Conclusions:

• The study provides quantitative insights into the C-H bond activation mechanism by CrO2+.
• Spin inversion has a minor but notable effect on the reaction energetics.
• Comparative analysis with CrO+ suggests potential influences of ligation on reactivity.