Highly polar stacking interactions wrap inorganics in organics: lone-pair-π-hole interactions between the PdO4 core and electron-deficient arenes

Cocrystallization of the palladium acetate cluster Pd-3(OAc)(6) (abbreviated as [Pd-3]) with electron-deficient iodine(i)-based perfluoroarenes ((ArI)-I-F: iodopentafluorobenzene, 4-iodoheptafluorotoluene, 1,4-diiodotetrafluorobenzene, 1,2-diiodotetrafluorobenzene, and octafluoro-4,4 '-diiodo-1,1-biphenyl) and iodine-free octafluoronaphthalene gave a series of six cocrystals [Pd-3]center dot(arene) studied by single-crystal X-ray diffractometry. Significant intermolecular noncovalent interactions were verified by a density functional theory study, molecular electrostatic potential and Hirshfeld surface analyses, a combined QTAIM/NCPlot approach, and NBO and energy framework calculations. In five out of six structures, the aromatic rings coupled with cluster [Pd-3] via lone pair-pi-(Ar-F)-hole interactions. The iodine-containing arenes, (ArI)-I-F, were additionally involved in halogen bonding with carboxylate O centers, but inorganic-organic stacking still remained the structure-determining interaction. In the stacking, the electron-rich PdO4 plane behaved as a five-center nucleophile providing oxygen lone pairs in addition to the d(z)(2)-Pd-II orbital; this plane complemented the pi-acidic surface of the arenes, affording highly polar circular stacking, where organics wrapped inorganics.

Automated summary

The study revealed that cocrystallization of iodine(i)-based perfluoroarenes with palladium acetate cluster resulted in significant noncovalent interactions, as confirmed by single-crystal X-ray diffractometry. In the structures, aromatic rings were coupled with the cluster through lone pair-pi-(Ar-F)-hole interactions, while iodine-containing arenes were engaged in halogen bonding with carboxylate O centers. The electron-rich PdO4 plane behaved as a nucleophile providing oxygen lone pairs, complementing the pi-acidic surface of the arenes in circular stacking.