On the Unusual Weak Intramolecular C center dot center dot center dot C Interactions in Ru-3(CO)(12): A Case of Bond Path Artifacts Introduced by the Multipole Model?

作者：Farrugia Louis J^*; Senn Hans Martin

来源：Journal of Physical Chemistry A, 2012, 116(1): 738-746.

DOI：10.1021/jp2100039

In a recent publication in this journal, an experimental charge density analysis on the triruthenium cluster Ru-3(CO)(12) showed unusual C center dot center dot center dot C bond paths linking the axial carbonyl ligands [Gervasio, G.; Marabello, D.; Bianchi, R.; Form, A. J. Phys. Chem, A 2010; 1.14, 9368, hereafter GMBF]. These were also observed in one theoretical DFT calculation, and are associated with very low values of rho(r(b)) and del(2)rho(r(b)). Our independent experimental charge density analysis on Ru-3(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 center dot center dot center dot 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 center dot center dot center dot C bond paths between the axial carbonyl ligands in the derived molecular graphs. On the other hand,. using the experimental structure factors to generate %26quot;experimental%26quot; X-ray constrained DFT wave functions once again yields molecular graphs which do not show these secondary C center dot center dot center dot 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 rho(r(b)) and del(2)rho(r(b)) are very low.

• 出版日期2012-1-12