Abstract: A crystal of palladium(II) bis(acetylacetonate), Pd(κ2O,O'-CH3COCHCOCH3)2 (1), has been studied by high-precision X-ray diffraction followed by topological analysis of the electron density distribution function, ρ(r). Electron microscopy studies have revealed growth-related specific morphological properties that may affect high-angle X-ray diffraction data. The analysis of ρ(r) in the crystal within the QTAIM framework has provided values of bond energies, atomic charges and atomic volumes. The charge redistribution in the complex points out to a predominantly covalent character of the Pd-acac bond (~117 kcal/mol). Results of experimental electron density studies and DFT calculations for the crystal both indicate that the Pd-acac interaction should be best described as a bis peak-to-hole interaction, where electron-deficient sites are located at the Pd atom and directed towards the oxygen atoms. Gas-phase DFT geometry optimization at the PBE0 / def2-TZVP level of theory reproduces the bond distances and bond angles well, but demonstrates the flat geometry of the complex. It has been confirmed that the dominant non-covalent intermolecular π-π stacking interaction slightly perturbs planarity of the complex in the crystal. Both DFT methods and QTAIM-based approaches have been used to evaluate the crystal lattice energy and the energy of the π-π stacking interaction. The energy contribution of the latter to the lattice energy is ~50%.

Cite: Stash A.I. , Ivanova N.M. , Minyaev M.E.
Aspects of bonding in Pd(acac)2 from experimental and theoretical studies based on high-precision X-ray diffraction data
Journal of Molecular Structure. 2026. V.1381. 147770 . DOI: 10.1016/j.molstruc.2026.147770 Scopus OpenAlex

Dates:

Submitted:	Jun 26, 2026
Accepted:	Oct 1, 2026
Published online:	Oct 2, 2026

Identifiers:

≡ Scopus:	2-s2.0-105052557603
≡ OpenAlex:	W7215853167

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