Regium bonds between MCN (M = Cu, Ag, Au) and organic halocarbons

A theoretical study was performed on the regium bonds formed in the complexes of C spn -X···MCN ( n = 1–3; X = F, Cl, Br and I; M = Cu, Ag and Au) Systems at the MP2/aug-cc-pVTZ level. When halocarbons act as Lewis bases to provide lone pair electrons, regium bonds are formed, with the contribution of polarization energy increasing with the electron-withdrawing ability of the carbon hybrid type and the atomic radius of the halogen atom. Meanwhile, regium bonds in the C spn -X···MCN system exhibit partially covalent properties, which are affected by substitution and hybridization effects to some extent. Natural bond orbital (NBO) analysis, atoms in molecules (AIM) C spn -X···MCN calculations, and basis set superposition error (BSSE) correction were performed for these complexes. NBO results show that charge transfer (0.0245–0.3241 e) is positively correlated with interaction energy; AIM analysis confirms that electrostatic interaction is the main driving force for the stability of regium-bonded complexes, with BSSE correction values ranging from 0.52 to 2.37 kcal/mol, ensuring the reliability of interaction energy data.