Perthio- and Perseleno-1,3-butadienes, -but-1-ene-3-ynes, and -[3]-cumulenes:  One-Step Syntheses from 1,4-Dilithio-1,3-butadiyne

Treatment of 1,4-dilithio-1,3-butadiyne (1) with dichalcogenides RSSR or RSeSeR affords dithio- and diseleno-1,3-butadiynes (2, 3), perthio- and perseleno-[3]-cumulenes (4, 5), perthio- and perseleno-1,3-butadienes (6, 7), and/or perthio- and perseleno-but-1-ene-3-ynes (8, 9). The products can be controlled by stoichiometry and temperature, by the presence or absence of oxygen, and by choice of the “R” group. By X-ray crystallography, hexa(methylthio)-1,3-butadiene is highly twisted, with a torsion angle [Φ(CCCC)] of 84.7° and an elongated C(2)−C(3) distance of 1.484(3) Å.