Bis(phenylthio)acetylene – monomer of a polythioacetylene

Abstract

Abstract The crystal structure of bis(phenylthio)acetylene, C14H10S2, was studied by X-ray diffraction at 87 K. The space group is P21/c, a = 14.6790(8) Å, b = 5.6481(3) Å, c= 14.7115(11) Å, β= 105.60(1)° from repeated centrings on resolved MoK α 1 peaks, Z = 4. Intensity data were collected with MoKα radiation on three different crystals, LO data with (sinθ)/λ < 0.714 Å−1 on one crystal, and HO data in the (sinθ)/λ range 0.682–0.857 Å−1 on two different crystals. The standard corrections were applied to the data, including corrections for absorption, before merging. Structure solution was by direct methods, refinement based on the full data set, 5757 F o converged at Rw = 0.036, a separate refinement including only non-hydrogen atoms and based on 3206 F o with (sin θ/λ > 0.65 Å−1 gave a final Rw = 0.031. The atomic sequence –S–C≡C–S– is distinctly nonlinear, the S–C (acetylene) bonds, average 1.6647(9) Å, have significant double bond character, and the central C≡C bond, 1.2224(12) Å, is about 0.04 Å longer than expected for a vicinally substituted carbon-carbon triple bond. The pattern of angular deviations from 120° in the phenyl rings shows that the S atoms are electronegative substituents combining σ-electron withdrawal with some π-electron donation. Both phenyl groups are nearly eclipsed with the acetylenic moiety which gives rise to two short intramolecular H(phenyl)…C(acetylene) contacts, 2.49 Å and 2.59 Å.