Kameji Yamane

Structure of azuleno[1,2-b]thiophene

C12H8S, m.p. 375-376 K, orthorhombic, Pnma, a = 7.954 (2), b = 19.194 (5), c = 6.021 (2) A, D m = 1.33, D x = 1.332 Mg m -3, Z = 4. Final R = 0.105 for 504 reflexions. The molecules form a sheet parallel to (010). The sheets are stacked along b. The structure is disordered as in azulene. The molecule is planar within 0.06 (2)A. The bond-length alternation in the seven-membered ring is significant, the shortest C-C length being 1.27 (2) A between positions 5 and 6 (C(7)-C(8)), and the longest 1.58 (2)A between 4a and 9a (C( 11)-C(12)). 1.2 + 0.15 tan 0) using Ni-filtered Cu radiation (2 = 1.5418 A) at 40 kV and 200 mA. Background was measured for 5 s on either side of the peak. Three reference reflexions showed no intensity deterioration. The intensities were corrected for Lorentz and polarization factors, but not for absorption (p(Cu Kct) = 2.59 mm-l). In total 587 independent reflexions were collected, of which 504 with IFol > o(F) were used in the refinement. The structure was solved by the Patterson method. At first the space group was assumed to be Pn21a based on the molecular symmetry and Z = 4. A