Unexpected Formation of the Iodobismuthate Salt (C₁₄H₁₅S₂N₂)₂(C₉H₁₀SN)₂[Bi₄I₁₆] upon Reaction of the Unsaturated Ligand Z-PySCH₂CH=CHCH₂SPy with BiI₃

The olefinic dithioether (Z)-1,4-bis(pyridin-2-ylthio)but-2-ene Z-PyS(CH2CH=CHCH2)SPy (L) was prepared by the treatment of cis-ClCH2CH=CHCH2Cl with in situ generated potassium pyridine-2-thiolate Py-SK and analyzed by IR and NMR spectroscopy. To investigate the chemistry of polynuclear iodobismuthate complexes, two equivalents of BiI3 were reacted with L in the MeOH solution to afford the anionic tetranuclear title compound (C14H15S2N2)2(C9H10SN)2[Bi4I116] with a N-protonated (Z)-1,4-bis(pyridin-2-ylthio)but-2-ene as a counterion. Compound 1 was characterized by IR and UV spectroscopy; the formation of a tetranuclear framework was ascertained by a single-crystal X-ray diffraction study performed at 100 K. Furthermore, an unusual Bi(III)-meditated cyclization of one Z-PyS(CH2CH=CHCH2)SPy ligand occurred, affording the bicyclic pyridinium salt 3-vinyl-2,3-dihydrothiazolo[3,2-a]pyridinium bearing a terminal vinyl group, compensating the second negative charge of the Bi4I164− cluster anion. The SCXRD characterization was completed by a Hirshfeld surface analysis, revealing some secondary interactions occurring in the crystal.