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Metal–ligand cooperative action gives opportunity for sodium atoms to participate in metallacycloaddition with isoselenocyanates.

New complex compounds [Cd(μ-L1)2]n (I), [Cd(μ-L2)(μ-Cl)(μ-DMSO)]n (III), and [Cd2(μ-L2)(μ-Cl)3(μ-DMSO)DMSO/EtOH]n (IV) are synthesized by the reactions of 1-(4-methoxyphenyl)-1,4-dihydro-5H-tetrazole-5-thione (HL1) and 1-(2-methoxyphenyl)-1,4-dihydro-5H-tetrazole-5-thione (HL2) with cadmium chloride. The molecular and crystal structures of the complexes are determined by X-ray structure analysis (CIF files CCDC nos. 1993455 (I), 1869249 (III), and 1993497 (IV)). Complexes I, III, and IV have uniform polymeric structures. The О···Н, Cl···H, and C···S contacts are observed between 1D polymeric chains in the crystal cells of complexes I, III, and IV. Complexes III and IV contain DMSO molecules. Under other equivalent conditions, the reaction of HL1 or HL2 with cadmium chloride in ethanol affords complex I or II of different compositions. Complex II contains the chlorine atom as found by scanning electron microscopy, whereas no chlorine is observed in complex I according to the X-ray structure analysis data.

Three new organoselenium compounds are synthesized: N-phenyl-2-(2-thienylacetyl)hydrazinecarboselenoamide (I), 4-phenyl-5-(2-thienylmethyl)-2,4-dihydro-3H-1,2,4-triazole-3-selone (II), and 3,3'-di[4-phenyl-5-(2-thienylmethyl)-4H-1,2,4-triazolyl] diselenide (III). Two of them (compounds II and III) are characterized by X-ray diffraction analysis (CIF files CCDC nos. 1956602 (II) and 1956603 (III)). Compound II crystallizes in the monoclinic crystal system (space group P21/n) with two crystallographically independent molecules A and B being different conformers relative to rotation about the NTrz–CTrz–C(H2)–CTph bond, where Trz is triazole and Tph is thiophene (gauche-A (51.4(3)°) and cis-B (4.2(4)°)). In the crystal of compound II, molecules A and B form chains along the crystallographic axis a due to strong hydrogen bonds N–H···Se. Then the chains are bound into a three-dimensional framework via intermolecular nonvalent interactions Se···S (3.3857(11) A). Owing to the anomeric effect, diselenide III is characterized by the typical gauche conformation of the substituents at the Se–Se bond (torsion angle СSeSeС 83.5(4)°) stabilized by a weak intramolecular hydrogen bond С–H···π. In the crystal of compound III, the molecules form chains along the crystallographic acid b due to intermolecular noncovalent interactions Se···π(C–C) (3.404(6) and 3.458(12) A), Se···Se (3.8975(11) A), and S···N (3.250(5) A). Bactericidal and fungicidal activity of the synthesized compounds is studied.

In the crystal of the title compound, C7H5FN4S, the molecules are non-planar, with dihedral angle formed by least-squares planes of tetrazole and benzene rings of 59.94 (8) °. The crystal packing is formed by N—H...S hydrogen bonds, which link the molecules into centrosymmetric dimers with an R 2 2(8) ring motif, and by the offset face-to-face π–π stacking interactions between the benzene rings, which join the dimers into layers parallel to (100). The Hirshfeld surface analysis shows that the most important contributions to the surface contacts are from N...H/H...N (21.9%), S...H/H...S (21.1%), H...H (14.6%), F...H/H...F (11.8%) and C...H/H...C (9.5%) interactions.

The reaction of (–)-cytisine with 2-(chloroselanyl)pyridine-1-oxide afforded the corresponding selenenylamide. Its biological activity against Aspergillus oryzae micromycetes was revealed.

Compound 4-(2-methoxyphenyl)-5-(thiophen-2-ylmethyl)-2,4-dihydro-1H-1,2,4-triazole-3-thione (LН) and its complex with cadmium(II) C42.12H39.50N9O3.12S6Cl2Cd (I) are synthesized. Their molecular and crystal structures are determined by X-ray diffraction analysis (СIF files CCDC nos. 1835776 (LН) and 1547251 (I)). Free ligand LН is thione and in the crystal forms H-bonded centrosymmetric dimers by two hydrogen bonds N–H···S. Complex I has a distorted trigonal bipyramidal structure: the sulfur atoms lie in the base and the chlorine atoms occupy the axial positions. Compound LН manifests itself as a monodentate ligand (S) when forming complex I and retains the thione form. The molecule of complex I is stabilized due to strong intramolecular contacts N–H···Cl. The crystal packing of compounds LН and I is formed due to the intermolecular contacts C–H···π, H···S, H···O, and H···N.

Cadmium (C20H16Cd2N4O4Se4) (I) and nickel (C10H8N2NiO2Se2) (II) selenolates are synthesized by the exchange reactions of sodium 1-oxypyridyl-2-selenolate and cadmium(II) and nickel(II) chlorides. The molecular and crystal structures of the complexes are determined by X-ray structure analysis (CIF files CCDC nos. 1585246 (I) and 1585251 (II)). Complex I forms a centrosymmetric dimer in which the coordination polyhedron of the cadmium atom is a distorted trigonal bipyramid and the selenium atoms take the trans configuration. Complex II containing the solvate C2H5OH molecule has a square structure and is a monomer. Unlike complex I, in complex II the selenium atoms of the ligands take the cis configuration. The crystal packings in complexes I and II are formed by weak intermolecular hydrogen bonds C–H···O and C–H···Se.

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).

The molecular and crystal structures of 1-(2-methoxyphenyl)-1,4-dihydro-5H-tetrazole-5-thione (L) and its complex with cadmium(II) (II) are studied by X-ray diffraction analysis (CIF files CCDC nos. 1567109 (L) and 1547252 (II)). Free ligand L is nonplanar thione. The dihedral angle between the tetrazole and benzene cycles is 85.21(7)°. These cycles form centrosymmetric dimers in the crystal by two hydrogen bonds N–H···S. The dimers contain the central planar eight-membered ring {S=C–N–H···S=C–N–H···}. Complex II has a chain structure of the composition [(C8H7N4OS)2Cd]n. The coordination mode of the Сd(II) atom is a distorted tetrahedron consisting of two nitrogen atoms and two sulfur atoms of four ligands L. The 1D chains contain the eight-membered rings {←S=C–N–Cd ← S=C–N–Cd} in the boat conformation. Weak intermolecular hydrogen bonds C–H···N are observed between the adjacent 1D chains along the c axis in the crystal.

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 crystal via SeN chalcogen bonding, which was studied theoretically.

The molecular and crystal structures of 1-(4-fluorophenyl)-1,4-dihydro-1H-tetrazole-5-thione (I) and its complex with cadmium(II) (II) are studied by single crystal XRD. Free ligand I is thione; it has a nonplanar structure (the torsion angle between the tetrazole and benzene rings is 54.99(7)°) and forms H-bonded centrosymmetric dimers via two N–H…S hydrogen bonds in the crystal. The dimers contain a central planar eight-membered {S=C–N–H…S=C–N–H…} ring. Complex II has a chain structure with the composition [(C7H4N4FS)2Cd]n. The environment of the Cd(II) atom consists of two nitrogen atoms and two sulfur atoms from four ligands I and represents a distorted tetrahedron. When complex II forms, ligand I converts into the thiol form. Infinite 1D chains contain eight-membered {←S=C–N–Cd←S=C–N–Cd} rings in a chair conformation. The chains in the crystal are arranged in layers parallel to the (101) plane due to secondary intermolecular F…F and π–π-stacking interactions.

A reaction of dimethyl bicyclo[2.2.2]oct-5-ene-endo-2,endo-3-dicarboxylate with 1,3-benzо- thiazole-2- and 3-methoxycarbonylpyridine-2-sulfenyl chlorides leads to two types of heterocyclization products, which are formed through the ring closure by the oxygen atom of the carbоmethoxy group and/or by the nitrogen atom of the hetaryl fragment of the sulfenylating agent. The product ratio is affected by the medium nature and structural features of sulfenyl chlorides.

The title compound 4-(3-methoxyphenyl)-3-(2-thienylmethyl)-4,5-dihydro-3H-1,2,4-triazole-3-selone 2 was synthesized by two-step procedure including condensation of 1-isoselenocyanato-3-methoxybenzene with 2-(2-thienyl)acetohydrazide to selenosemicarbazide 1 and its intramolecular cyclization. Oxidation of selone 2 by atmospheric oxygen or hydrogen peroxide furnished corresponding diselenide 3 or product of elimination of selenium 1,2,4-triazole 4. Alkylation of compound 2 by benzyl chloride leads to the formation of selenide 5. The synthesized compounds have been characterized by spectroscopic techniques and the structures of 3,4 and 5 were confirmed by X-ray diffraction techniques and the supramolecular contacts were analyzed by Hirshfeld surface analyses.

Correction for ‘Novel cationic 1,2,4-selenadiazoles: synthesis via addition of 2-pyridylselenyl halides to unactivated nitriles, structures and four-center Se⋯N contacts’ by Victor N. Khrustalev et al., Dalton Trans., 2021, 50, 10689–10691, DOI: 10.1039/D1DT01322J.

Novel S- and Se-containing terpenoids were prepared by reacting (+)-camphene with N-heterocyclic selenyland sulfenyl chlorides.