Synergistic and Diminutive Effects between Regium and Aerogen Bonds.

The aerogen bond is formed in complexes of HCN-XeF2 O and C2 H4 -XeF2 O. 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 C2 H4 . The coinage substitution strengthens the aerogen bond in MCN-XeF2 O (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 C2 H2 -MCN-XeF2 O and C2 H4 -MCN-XeF2 O, but is weakened by the regium bond in MCN-C2 H4 -XeF2 O and C2 (CN)4 -MCN-XeF2 O. 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.