The Structure Of Dichlorotris(Triphenylphosphine)Ruthenium(Ii): A Dft Study Of Interaction Energies And Substitution Mechanism

The structure and substitution energies of dichlorotris(triphenylphosphine)ruthenium(II) complex, [RuCl2(PPh3)(3)], was computed with ten different methods at the density functional theory level using a composition of basis sets. The PBE0 functional led to the best description of bond lengths, while the MN12-L functional yielded the best results for bond angles. For calculation of the Ru-P bond dissociation energies, the best results were obtained with the M06-L functional. The nature of the Ru-P bond was discussed in terms of donation and back-donation as well as in terms of the steric versus covalent contributions to the bonding. In the square pyramidal structure, the apical Ru-P bond is considerably tighter than the basal Ru-P bonds. This is due to an interaction of the apical PPh3 ligand with a high d character orbital on the Ru atom, favouring back-donation, leading to a short Ru-P distance and strong bonding energy. Additionally, we also investigated the equilibrium structures and mechanism for the substitution of one of the PPh3 group by the piperidine molecule. The equilibrium between the several species involved in the substitution process indicates that addition of the piperidine molecule to [RuCl2(PPh3)(3)] followed by elimination of a PPh3 unity is the pathway with lower energy.