On the unusual weak intramolecular C...C interactions in Ru₃(CO)₁₂: a case of bond path artefacts introduced by the multipole model?

Farrugia, L.J. and Senn, H.M. (2012) On the unusual weak intramolecular C...C interactions in Ru₃(CO)₁₂: a case of bond path artefacts introduced by the multipole model? Journal of Physical Chemistry A, 116(1), pp. 738-746. (doi: 10.1021/jp2100039)

Abstract

In a recent publication in this journal, an experimental charge density analysis on the triruthenium cluster Ru₃(CO)₁₂ showed unusual C...C bond paths linking the axial carbonyl ligands [Gervasio, G.; Marabello, D.; Bianchi, R.; Forni, A. J. Phys. Chem. A 2010, 114, 9368, hereafter GMBF]. These were also observed in one theoretical DFT calculation, and are associated with very low values of ρ(<b>r</b>_b) and ²ρ(<b>r</b>_b). Our independent experimental charge density analysis on Ru₃(CO)₁₂ is entirely consistent with GMBF and confirms the presence of these apparent weak interactions in the multipole model density. However, we conclusively demonstrate that these unusual C...C bond paths between the axial carbonyl ligands are in fact artifacts arising from the Hansen-Coppens multipole model, which is used to analyze the experimental data. Numerous relativistic and nonrelativistic gas-phase DFT calculations, using very extensive basis sets and with corrections for dispersion effects, uniformly fail to reproduce these intramolecular features in the QTAIM topology of the electron density. Moreover, multipole fitting of theoretical static structure factors computed from these quantum electron densities results in the reappearance of the C...C bond paths between the axial carbonyl ligands in the derived molecular graphs. On the other hand, using the experimental structure factors to generate “experimental” X-ray constrained DFT wave functions once again yields molecular graphs which do not show these secondary C...C bond paths. The evidence therefore strongly implicates the multipole model as the source of these spurious features and in turn suggests that great caution should be applied in the interpretation of bond paths where the values of ρ(<b>r</b>_b) and ²ρ(<b>r</b>_b) are very low.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Farrugia, Dr Louis and Senn, Dr Hans
• Authors: Farrugia, L.J., and Senn, H.M.
• Subjects: Q Science > QD Chemistry
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of Physical Chemistry A
• Journal Abbr.: J. Phys. Chem. A
• Publisher: American Chemical Society
• ISSN: 1089-5639
• ISSN (Online): 1520-5215
• Published Online: 01 November 2011