Electron-structure calculations and bond order analysis using density functional theory of cationic dinuclear arene ruthenium complexes

The structure and nature of the metal-metal bonding interaction in the cationic complexes (eta6-C6Me6)2Ru2(mu2-H)3]+ (1), (eta6-C6Me6)2Ru2(mu2-H)2(mu2-1,4-SC6H4Br)]+ (2), (eta6-C6Me6)2Ru2(mu2-H)(mu2-1,4-SC6H4Br)2]+ (3), and (eta6-C6Me6)2Ru2(mu2-1,4-SC6H4Br)3]+ (4) have been studied at the density functional theory (DFT) level using molecular orbital (MO) theory, bond order (BO) analysis, bond decomposition energy (BDE), electron localization function (ELF), and Laplacian of the density methods. The results show that there is no direct bond between the two ruthenium atoms in 1-4, the MO interaction within the diruthenium backbone being stabilized by the bridging ligands. For complex 1, the ELF clearly shows that the bond within the diruthenium backbone is through the three bridging hydride ligands, which act as a sort of glue by forming three-center two-electron bonds characterized by (Ru, H, Ru) basins with 1.8 e mostly located in the H atomic basin.