Crystal structure of rac-(3aR∗,9aS∗)-4,4,4-trichloro-1,2,3,3a,4,9a-hexahydro-4λ5,9λ4-cyclopenta[4,5][1,3]tellurazolo-[3,2-a]pyridine

The title compound, C10H12Cl3NTe, crystallizes with two crystallographically independent molecules (A and B) in the asymmetric unit. In each case, the coordination around the Te atom is distorted square-pyramidal, with the equatorial plane composed of the three Cl atoms and the C atom of the pyridinium ring. The Te atom is displaced from the meansquare plane by 0.1926 (7) and 0.1981 (8) Å, in molecules A and B, respectivly, away from the apical C atom. The bond lengths from the Te atom to the two Cl atoms arranged trans to each other [2.5009 (7)/2.5145 (7) and 2.5184 (7)/2.5220 (8) Å in molecules A and B, respectivly] are substantially shorter than the third Te-Cl distance [2.8786 (7) and 2.8763 (7) Å in molecules A and B, respectivly]. The 1,3-tellurazole ring is almost planar (r.m.s. deviations of 0.042 and 0.045 Å in molecules A and B, respectivly). The cyclopentane rings in both molecules A and B adopt envelope conformations with the carbon atom opposed to the (Te)C-C(N) bond as the flap. In the crystal, molecules form centrosymmetric 2 + 2 associates via Te· ··Cl interactions [3.3993 (7) and 3.2030 (7) Å]. As a result of these secondary interactions, the Te atom attains a strongly distorted 5 + 1 octahedral environment. Further, the 2 + 2 associates are bound by weak C-H···Cl hydrogen bonds into a three-dimensional framework

Crystal structure of rac-(3aR∗,9aS∗)-4,4,4-trichloro-1,2,3,3a,4,9a-hexahydro-4λ5,9λ4-cyclopenta[4,5][1,3]tellurazolo-[3,2-a]pyridine

The title compound, C10H12Cl3NTe, crystallizes with two crystallographically independent molecules (A and B) in the asymmetric unit. In each case, the coordination around the Te atom is distorted square-pyramidal, with the equatorial plane composed of the three Cl atoms and the C atom of the pyridinium ring. The Te atom is displaced from the meansquare plane by 0.1926 (7) and 0.1981 (8) Å, in molecules A and B, respectivly, away from the apical C atom. The bond lengths from the Te atom to the two Cl atoms arranged trans to each other [2.5009 (7)/2.5145 (7) and 2.5184 (7)/2.5220 (8) Å in molecules A and B, respectivly] are substantially shorter than the third Te-Cl distance [2.8786 (7) and 2.8763 (7) Å in molecules A and B, respectivly]. The 1,3-tellurazole ring is almost planar (r.m.s. deviations of 0.042 and 0.045 Å in molecules A and B, respectivly). The cyclopentane rings in both molecules A and B adopt envelope conformations with the carbon atom opposed to the (Te)C-C(N) bond as the flap. In the crystal, molecules form centrosymmetric 2 + 2 associates via Te· ··Cl interactions [3.3993 (7) and 3.2030 (7) Å]. As a result of these secondary interactions, the Te atom attains a strongly distorted 5 + 1 octahedral environment. Further, the 2 + 2 associates are bound by weak C-H···Cl hydrogen bonds into a three-dimensional framework

An unusually stable pyridine-2-selenenyl chloride: structure and reactivity

According to an X-ray diffraction study, pyridine-2-selenenyl chloride (1) characterized by unusually high stability both in solutions and in the solid state adopts a dimeric structure formed by two secondary intermolecular Se···N interactions. However, it slowly transforms into zwitterionic T-shaped pyridinium-2-selenenyl dichloride (2) in a dichloromethane solution. Conformational features, electronic structures, and reactivities of 1 and 2 are discussed on the basis of experimental and theoretical (quantum chemical calculations) data. © 2016, Springer Science+Business Media New York

Bromination of bis(pyridin-2-yl) diselenide in methylene chloride: The reaction mechanism and crystal structures of 1H-pyridine-2-selenenyl dibromide and its cycloadduct with cyclopentene(3aSR,9aRS)-2,3,3a,9a-tetrahydro-1H-cyclopenta[ 4,5][1,3]selenazolo[3,2-a]pyridinium bromide

1H-Pyridine-2-selenenyl dibromide, C5H5NSeBr2, 1, is a product of the bromination of bis(pyridin-2-yl) diselenide in methylene chloride recrystallization from methanol. Compound 1 is essentially zwitterionic: the negative charge resides on the SeBr2 moiety and the positive charge is delocalized over the pyridinium fragment. The C - Se distance of 1.927(3)Å is typical of a single bond. The virtually linear Br - Se - Br moiety of 178.428(15)° has symmetrical geometry, with Se - Br bonds of 2.5761(4) and 2.5920(4)Å, and is twisted by 63.79(8)° relative to the pyridinium plane. The Se atom forms an intermolecular Se⋯Br contact of 3.4326(4)Å, adopting a distorted square-planar coordination. In the crystal, molecules of 1 are linked by intermolecular N - H⋯Br and C - H⋯Br hydrogen bonds, as well as by non-covalent Se⋯Br interactions, into a three-dimensional framework. (3aSR,(9aRS)-2,3,3a,9a-Tetrahydro-1H-cyclopenta[4,5][1,3]selenazolo[3,2-a]pyridinium-9 bromide, C10H12NSe + ·Br - , 2, is a product of the cycloaddition reaction of 1 with cyclopentene. Compound 2 is a salt containing a selenazolopyridinium cation and a bromide anion. Both five-membered rings of the cation adopt envelope conformations. The dihedral angle between the basal planes of these rings is 62.45(11)°. The Se atom of the cation forms two additional non-covalent interactions with the bromide anions at distances of 3.2715(4) and 3.5683(3)Å, attaining a distorted square-planar coordination. In the crystal, the cations and anions of 2 form centrosymmetric dimers by non-covalent Se⋯Br interactions. The dimers are linked by weak C - H⋯Br hydrogen bonds into double layers parallel to (001). © 2019

An unusually stable pyridine-2-selenenyl chloride: structure and reactivity

According to an X-ray diffraction study, pyridine-2-selenenyl chloride (1) characterized by unusually high stability both in solutions and in the solid state adopts a dimeric structure formed by two secondary intermolecular Se···N interactions. However, it slowly transforms into zwitterionic T-shaped pyridinium-2-selenenyl dichloride (2) in a dichloromethane solution. Conformational features, electronic structures, and reactivities of 1 and 2 are discussed on the basis of experimental and theoretical (quantum chemical calculations) data. © 2016, Springer Science+Business Media New York

Erratum: Novel cationic 1,2,4-selenadiazoles: synthesisviaaddition of 2-pyridylselenyl halides to unactivated nitriles, structures and four-center Se⋯N contacts (Dalton Transactions (2021) 50 (10689-10691) DOI: 10.1039/D1DT01322J)

The authors regret that funding information was omitted from the original publication of this paper. Funding for this research was provided by RFBR (project number 21-53-54001) and RUDN University Strategic Academic Leadership Program. This study was supported by the VAST under grant no. QTRU01.04/21-22. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © The Royal Society of Chemistry 2021

Novel cationic 1,2,4-selenadiazoles: synthesisviaaddition of 2-pyridylselenyl halides to unactivated nitriles, structures and four-center Se⋯N contacts

2-Pyridylselenyl halides undergo facile coupling with a triple CN bond of unactivated nitriles. Unprecedented heterocyclization allowed the preparation of a novel class of cationic 1,2,4-selenadiazoles in remarkably high yields. Cationic 1,2,4-selenadiazoles form supramolecular dimers in the crystalviaSe⋯N chalcogen bonding, which was studied theoretically. © The Royal Society of Chemistry 2021

2-Pyridylselenenyl versus 2-Pyridyltellurenyl Halides: Symmetrical Chalcogen Bonding in the Solid State and Reactivity towards Nitriles

The synthesis of 2-pyridyltellurenyl bromide via Br2 oxidative cleavage of the Te–Te bond of dipyridylditelluride is reported. Single-crystal X-ray diffraction analysis of 2-pyridyltellurenyl bromide demonstrated that the Te atom of 2-pyridyltellurenyl bromide was involved in four different noncovalent contacts: Te⋯Te interactions, two Te⋯Br ChB, and one Te⋯N ChB contact forming 3D supramolecular symmetrical framework. In contrast to 2-pyridylselenenyl halides, the Te congener does not react with nitriles furnishing cyclization products. 2-Pyridylselenenyl chloride was demonstrated to easily form the corresponding adduct with benzonitrile. The cyclization product was studied by the single-crystal X-ray diffraction analysis, which revealed that in contrast to earlier studied cationic 1,2,4-selenadiazoles, here we observed that the adduct with benzonitrile formed supramolecular dimers via Se⋯Se interactions in the solid state, which were never observed before for 1,2,4-selenadiazoles. © 2021 by the authors