Bromination of bis-(pyridin-2-yl) diselenide in methyl-ene chloride: the reaction mechanism and crystal structures of 1 H-pyridine-2-selenenyl dibromide and its cyclo-adduct with cyclo-pentene (3a SR,9a RS)-2,3,3a,9a-tetra-hydro-1 H-cyclo-penta-[4,5][1,3]selenazolo[3,2- a]pyridinium bromide

Zhanna V Matsulevich; Julia M Lukiyanova; Vladimir I Naumov; Galina N Borisova; Vladimir K Osmanov; Alexander V Borisov; Maria M Grishina; Victor N Khrustalev

doi:10.1107/S2056989019004997

Bromination of bis-(pyridin-2-yl) diselenide in methyl-ene chloride: the reaction mechanism and crystal structures of 1 H-pyridine-2-selenenyl dibromide and its cyclo-adduct with cyclo-pentene (3a SR,9a RS)-2,3,3a,9a-tetra-hydro-1 H-cyclo-penta-[4,5][1,3]selenazolo[3,2- a]pyridinium bromide

Acta Crystallogr E Crystallogr Commun. 2019 Apr 25;75(Pt 5):675-679. doi: 10.1107/S2056989019004997. eCollection 2019 May 1.

Authors

Zhanna V Matsulevich¹, Julia M Lukiyanova¹, Vladimir I Naumov¹, Galina N Borisova¹, Vladimir K Osmanov¹, Alexander V Borisov¹, Maria M Grishina², Victor N Khrustalev²

Affiliations

¹ R.E. Alekseev Nizhny Novgorod State Technical University, Minin St, 24, Nizhny Novgorod, 603950 , Russian Federation.
² Inorganic Chemistry Department, Peoples' Friendship University of Russia (RUDN University), 6 Miklukho-Maklay St., Moscow 117198, Russian Federation.

Abstract

1H-Pyridine-2-selenenyl dibromide, C₅H₅NSeBr₂, 1, is a product of the bromination of bis-(pyridin-2-yl) diselenide in methyl-ene 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 inter-molecular Se⋯Br contact of 3.4326 (4) Å, adopting a distorted square-planar coordination. In the crystal, mol-ecules of 1 are linked by inter-molecular N-H⋯Br and C-H⋯Br hydrogen bonds, as well as by non-covalent Se⋯Br inter-actions, into a three-dimensional framework. (3aSR,(9aRS)-2,3,3a,9a-Tetra-hydro-1H-cyclo-penta[4,5][1,3]selenazolo[3,2-a]pyridinium-9 bromide, C₁₀H₁₂NSe⁺·Br^-, 2, is a product of the cyclo-addition reaction of 1 with cyclo-pentene. 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 inter-actions 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 inter-actions. The dimers are linked by weak C-H⋯Br hydrogen bonds into double layers parallel to (001).

Keywords: 2,3,3a,9a-tetrahydro-1H-cyclopenta[4,5][1,3]selenazolo[3,2-a]pyridinium-9 bromide; 2-pyridylselenenyl bromide; bis(pyridin-2-yl) diselenide; bromination; crystal structure; cycloaddition reaction; cyclopentene.