Synthesis, Crystal Structure, and Hirshfeld Surface Analysis of Hexachloroplatinate and Tetraclorouranylate of 3-Carboxypyridinium—Halogen Bonds and π-Interactions vs. Hydrogen Bonds

This work aimed to synthesize new platinum and uranium compounds with nicotinic acid. In this article we describe the synthesis of two new anionic complexes (HNic)2[PtCl6] and (HNic)2[UO2Cl4] using wet chemistry methods. The structure of the obtained single crystals was established by single-crystal X-ray diffraction. The Hirshfeld surface analysis of the obtained complexes and their analogue (HNic)2[SiF6] was carried out for the analysis of intermolecular interactions. Hydrogen bonds (H···Hal/Hal···H and O···H/H···O) make the main contribution to intermolecular interactions in all compounds. Other important contacts in cations in all compounds are H···H, C···H/H···C and C···Hal/Hal···C; in anions H···Hal/Hal···H. The Pt-containing complex has a halogen-π interaction and halogen bonds, but Si-containing complex has a π–π staking interaction; these types of interactions are not observed in the U-containing compound.