ИСТИНА

The interacting quantum atom (IQA) approach was employed to scrutinize the nature of metal···metal (M···M) interactions in dimers (MX)2 of hydrides (MH), fluorides (MF), and chlorides (MCl) of coinage metals (group 11 elements). The (MX)2 molecules were optimized at CCSD(T) level using the fourth-order scalar-relativistic Douglas–Kroll–Hess (DKH) Hamiltonian (DKH4-CCSD(T) method henceforth) and relativistic all-electron basis sets for all atoms. The calculations performed indicate that interactions between M atoms in dimers studied are really repulsive. The metallophilicity (the stabilizing interaction between metal atoms) is thus not exist in these complexes. The only exception is dimer (AuH)2 of C2h symmetry. The existence of the latter dimer on the potential energy surface of (AuH)2 is an unambiguous evidence of the metallophilic Au···Au interaction in this dimer. Energies of M···M as well as X1···X2 repulsions are significantly outweighed by much higher energies of the interaction of two M atoms with two X atoms favoring thus the dimerization of the corresponding MX. Analysis of electron density distributions in the dimers allows one to conclude that electron populations of M atoms apparently dictate the nature of M···M interactions and the binding M atoms in the studied complexes. There exist certain critical values of positive charges on M atoms, on exceeding which M···M interactions in these complexes become repulsive despite negative formation energies of such complexes, small M···M internuclear distances, and the existence of a bond critical point (BCP) between M atoms. The same is presumably valid for other complexes of coinage and other transition metals with short intermetallic contacts. The data obtained show that a comparison of internuclear M-M distances with the sum of the van der Waals radii of two transition metal atoms as well as the existence (the absence) of (3,-1) CP between M atoms are inappropriate criteria for solid decision about the existence or the nonexistence of the binding of M atoms.