Bis(phenylthio)acetylene - monomer of a polythioacetylene

The crystal structure of bis(phenylthio)acetylene, C14H10S2, was studied by X-ray diffraction at 87 K. The space group is P2(1)/c, a = 14.6790(8) Angs trom, b = 5.6481(3) Angstrom, c = 14.7115(11) Angstrom, beta = 105.60(1)deg rees from repeated centrings on resolved MoKalpha 1 peaks, Z = 4. Intensity data were collected with MoK<(alpha)over bar> radiation on three different crystals, LO data with (sin theta)/lambda < 0.714 Angstrom(-1) on one crys tal, and HO data in the (sin theta)/lambda range 0.682-0.857 Angstrom(-1) o n 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 conv erged at R-w = 0.036, a separate refinement including only non-hydrogen ato ms and based on 3206 F-o with (sin theta)/lambda > 0.65 Angstrom(-1) gave a final R-w = 0.031. The atomic sequence -S-C = C-S- is distinctly nonlinear , the S-C (acetylene) bonds, average 1.6647(9)Angstrom, have significant do uble bond character, and the central CEC bond, 1.2224(12) Angstrom, is abou t 0.04 Angstrom longer than expected for a vicinally substituted carbon-car bon triple bond. The pattern of angular deviations from 120 degrees in the phenyl rings shows that the S atoms are electronegative substituents combin ing sigma-electron withdrawal with some pi-electron donation. Both phenyl g roups are nearly eclipsed with the acetylenic moiety which gives rise to tw o short intramolecular H(phenyl)...C(acetylene) contacts, 2.49 Angstrom and 2.59 Angstrom.