Relativistic effects in bonding and isomerization energy of the superheavy roentgenium ( ₁₁₁Rg) cyanide

The cyanide and isocyanides of the superheavy roentgenium ( ₁₁₁Rg) element are investigated using relativistic 4-component Dirac-Fock (DF) and 2-component Density-Functional Theory (DFT) with ZORA Hamiltonian. The relativistic effects in bonding and energetics allow us to conclude that these complexes could be synthesized in a linear conformation with a preference for the RgCN isomer. The relativistic effects (RE) lead to an increase in the covalent character of the Rg(I)-ligand interaction, resulting in a higher charge transfer from the ligand to the metal by an enhanced acceptor character of Rg(I), mainly due to the relativistic stabilization of the 7s shell. The inclusion of the spin-orbit interaction modifies the bonding picture leading to a decrease of about 40 kcal/mol in the bonding interaction in both isomers. In conclusion, our calculations at several levels of theory suggest that it is possible to develop an exotic chemistry of complexes involving Rg(I) and the CN ^- ligand.