Mechanistic Insights into E(II)-Catalyzed (E = Si, Ge, Sn, Pb) C-F Activation/C-C Cross Coupling Reactions

This systematic computational study investigates carbodiphosphorane ligated E(II) (CDPE, E = Si, Ge, Sn, Pb) catalyzed hydrodefluorination (HDF) and C-C coupling reactions involving E(II)/E(IV) redox cycle. While CDPSn is known to catalyze HDF of pentafluoropyridine through sequential C-F oxidative addition (OA), F-H ligand metathesis (LM), and C-H reductive elimination (RE) steps, our density functional theory (DFT) calculations reveal distinct reactivity across the group. CDPSi undergoes C-F OA reaction but fails to proceed further, whereas CDPGe and CDPPb successfully complete the full catalytic cycle. Mechanistic analysis reveals that OA energy barriers are correlated with the nucleophilicity of the catalyst, LM energy barriers are primarily influenced by E-F bond strength, and RE energy barriers vary depending on the specific reaction pathway rather than following clear periodic trends. Although C-C coupling remains thermodynamically disfavored under standard conditions, the relevant energy substantially reduced through electronic tuning via electron-withdrawing substituents on the aryl ring. These findings provide a rational framework for designing main group catalysts, thereby advancing the field of main group catalysis.