Koordinacionnaâ himiâ

The reactions of oxovanadium(IV) sulfate with potassium salts of 2,3-, 2,4-, 2,5-, 3,4-, and 3,5-pyridinedicarboxylic acids (PdcH₂) and 2,2’:6’,2’’-terpyridine (Terpy) resulted in the formation of mononuclear heteroleptic complexes [VO(2,3-Pdc)(Terpy)] : 7H₂O (I), [VO(2,4-Pdc)(Terpy)] : 5H₂O (II), [VO(2,5-Pdc)(Terpy)] : 3H₂O (III), [VO(3,4-Pdc)(Terpy)(H₂O)] : 4H₂O (IV), [VO(3,5-Pdc)(Terpy)(H₂O)] : 7H₂O (V) и [VO(3,5-PdcH)(Terpy)(H₂O)](3,5-PdcH) : 2H₂O (VI), respectively. The structures of compounds I–VI were determined by single-crystal X-ray diffraction (CCDC nos. 2326828 (I), 2326829 (II), 2326830 (III), 2326831 (IV), 2326832 (V), 2440463 (VI)). In the structures of I–III, the acid dianions act as chelating ligands via the pyridine N atom and the O atom of one carboxyl group, while in compounds IV–VI, the acid anion is coordinated in the monodentate fashion. In the crystal packing of compounds I–III, intermolecular π–π-interactions between the heteroatomatic moieties of N-donor ligands are present, while in complexes IV and V, the intermolecular π–π-interactions involve also the pyridyl rings of dicarboxylate anions. Polycrystalline samples and solutions of complexes III and IV were characterized by EPR spectroscopy.

A new zinc(II) complex, LZnI₂, was obtained by the interaction of tridentate ligand 2,6-bis(5-(tert-butyl)-1H-pyrazol-3-yl)pyridine (L) with zinc(II) iodide. The compound was isolated in individual form and characterized using NMR spectroscopy and single-crystal X-ray diffraction (CIF file CCDC No. 2447394). The resulting complex exhibits catalytic activity in the reaction of CO₂ with substituted epoxides to form cyclic carbonates. This behavior is attributed to the simultaneous presence of a Lewis acidic metal center capable of coordinating the epoxide, a Lewis basic nitrogen site facilitating CO₂ binding, and a nucleophilic iodide anion that activates epoxide ring opening. The development of this approach to catalyst design may facilitate the creation of efficient systems for reactions of carbon dioxide with three-membered heterocycles.

The reaction between cobalt tetrafluoroborate hexahydrate with 2,2′-bipyridine (Вpy) and diphenylphosphinic acid leads to the formation of a new binuclear cobalt(II) complex [Co₂(µ-O₂PPh₂)₂(Вpy)₄](BF₄)₂ featuring sterically demanding bridging ligands. The synthesized complex was characterized by various physicochemical methods of analysis, the crystal structure was determined by X-ray diffraction. The analysis of the X-ray structure of the complex showed that the cobalt ions have a distorted octahedral coordination and are linked by bridges through two {µ-O₂PPh₂} fragments. The results of EPR spectroscopy and magnetochemical studies indicate the presence of a weak antiferromagnetic interaction between the cobalt ions in the molecule.