Elucidating the Mechanism of Simultaneous Activation of CH4 and CO2 Mediated by Single Group 10 Metal Anions in Gas Phase

Abstract

Quantum chemistry calculations predict that besides the reported single metal anion Pt^- , Ni^- can also mediate the co-conversion of CO₂ and CH₄ to form [CH₃ -M(CO₂ )-H]^- complex, followed by transformation to C-C coupling product [H₃ CCOO-M-H]^- (A), hydrogenation products [H₃ C-M-OCOH]^- (B) and [H₃ C-M-COOH]^- . For Pd^- , a fourth product channel leading to PdCO₂ ^- …CH₄ becomes more competitive. For Ni^- , the feed order must be CO₂ first, as the weaker donor-acceptor interaction between Ni^- and CH₄ increases the C-H activation barrier, which is reduced by [Ni-CO₂ ]^- . For Ni^- /Pt^- , the highly exothermic products A and B are similarly stable with submerged barrier that favors B. The smaller barrier difference between A and B for Ni^- suggests the C-C coupling product is more competitive in the presence of Ni^- than Pt^- . The charge redistribution from M^- is the driving force for product B channel. This study adds our understanding of single atomic anions to activate CH₄ and CO₂ simultaneously.

Keywords: CH4 activation; CO2 reduction; C−C coupling; quantum chemistry calculations; single metal anion.