C₄S₈^2- and C₁₆S₁₈^4-: Intermediates in the synthesis of poly(carbon sulfide)

(PPN)₂C₁₆S₁₈ was obtained by the addition of PPN⁺Cl^- to a methanolic extract of Na₂C₄S_x, derived from the reaction of C₆S₈O₂ and NaOMe. Centrosymmetric C₁₆S₁₈^4- consists of thiophene units unsymmetrically fused to two 1,4-dithiin rings. Solutions of C₁₆S₁₈^4- convert to C₈S₈^2- with heating. When C₄S_x (x ∼ 8) is reduced by Na/NH₃ followed by extraction and crystallization, one obtains the bicyclic polysulfide C₄S₈^2-, crystallized as its PPh₄⁺ salt.