Synergistic and Diminutive Effects between Regium and Aerogen Bonds

The aerogen bond is formed in complexes of HCN−XeF₂O and C₂H₄−XeF₂O. The lone pair on the N atom of HCN is a better electron donor in the aerogen bond than the π electron on the C=C bond of C₂H₄. The coinage substitution strengthens the aerogen bond in MCN−XeF₂O (M=Cu, Ag, and Au) and its enhancing effect becomes larger in the Au<Cu<Ag pattern. The aerogen bond is further enhanced by the regium bond in C₂H₂−MCN−XeF₂O and C₂H₄−MCN−XeF₂O, but is weakened by the regium bond in MCN−C₂H₄−XeF₂O and C₂(CN)₄−MCN−XeF₂O. Simultaneously, the regium bond is also strengthened or weakened in these triads. The synergistic and diminutive effects between regium and aerogen bonds have been explained by means of charge transfer and electrostatic potentials.