Ligand effects on oxidative methane activation by Fe(II)-complexes: Zwitterionic and anionic ligand environments are preferred over neutral and cationic for C[sbnd]H bond cleavage

Yildiz D. B., Sundholm D., DEDE Y.

Computational and Theoretical Chemistry, vol.1253, 2025 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 1253
  • Publication Date: 2025
  • Doi Number: 10.1016/j.comptc.2025.115414
  • Journal Name: Computational and Theoretical Chemistry
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Chimica, INSPEC
  • Keywords: Charged ligands, C–H bond cleavage, DFT, DLPNO-CCSD(T), Methane polarization, Oxidative methane activation
  • Gazi University Affiliated: Yes

Abstract

Quantum chemical calculations were performed on oxidative methane activation with Fe complexes, focusing on the influence of ligand environments on activation barriers. Various neutral and charged N-donor ligand environments were tested, revealing a clear relationship between ligand electrostatics and the C[sbnd]H cleavage barriers. Fe complexes of the zwitterionic and anionic ligands featured lower C[sbnd]H activation barriers than those of cationic and neutral ligands. Coordinated dioxygen is reduced at the initial complexation step for the zwitterionic and anionic ligands but not for the cationic ligands. The energy of the transition state of the C[sbnd]H bond breaking can further be lowered if the acidity of methane could be increased via a close lying positive charge. Domain-based local pair natural orbital coupled cluster singles doubles with perturbative triples (DLPNO-CCSD(T)) calculations were conducted. The M06-2X functional closely matched the DLPNO-CCSD(T) results.