The structure of dichlorotris(triphenylphosphine)ruthenium(II): a DFT study of interaction energies and substitution mechanism

ABSTRACT

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.

KEYWORDS:

• Ruthenium(II) complex
• coordination energy
• substitution mechanism
• agostic interaction
• energy decomposition

Acknowledgements

The authors thank CENAPAD-UFC for computational resource.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors would like to acknowledge CNPq (309080/2015-0 and 434955/2018-3), FAPERJ (E-26/203.001/2017, E-26/010.101118/2018, and E-26010.001424/2019), and the CAPES PRINT Program (88881.310460/2018-01) for financial support.