Fully relativistic (four-component) density-functional calculations were performed for the element 112 dimers (112)X (X = Pd, Cu, Ag and Au) and those of its lighter homolog, Hg. A relatively small decrease of about 15-20 kJ/mol in bonding was found from the HgX to (112)X compounds. Respectively, the bond lengths were increased by 0.06 Angstrom on the average. The Mulliken population analysis has shown this effect to be a result of a decreasing contribution of the relativistically stabilized 7s-AO of element 112 to bonding. The following trend in the binding energies was predicted for (112)X as a function of X: Pd > Cu > Au > Ag, exactly as the trend obtained experimentally for adsorption of Hg on the corresponding metal surfaces. (C) 2002 Elsevier Science B.V. All rights reserved.