SULFURANES .38. EVIDENCE FROM X-RAY CRYSTALLOGRAPHY FOR THE DIEQUATORIAL DISPOSITION OF A 5-MEMBERED RING IN A SULFURANE

The crystal and molecular structure of 1, 1-bis[1, 1, 1, 3, 3, 3-hexafluoro-2-phenyl-2-propanolato]-5-methyl-3, 3-bis(tri-fluoromethyl)[3H-2, 1-benzoxathiole], trialkoxysulfurane 8, was solved by X-ray crystallographic techniques. The compound crystallizes in space group P212121 of the orthorhombic system with four molecules in a cell of dimensions a = 19.74 (3), b = 14.20 (2), c = 10.74 (1) Å. The X-ray structure analysis (R = 0.099) reveals trigonal bipyramidal geometry around sulfur similar to structures previously determined for other sulfuranes. The five-membered ring including the sulfur atom is, however, clearly in the diequatorial orientation, 8. The axial S-O bond lengths are 1.840 (10) and 1.829 (10) Å while the equatorial SO and S-C bond lengths are 1.630 (9) and 1.777 (14) Å, respectively. The equatorial C-S-O angle is 95.0 (6)° while theO(apical)-S-O(apical) angle is 172.0 (4)° (bent away from the lone pair of electrons on sulfur). Observations are made concerning the relationship of structure with reactivity of 8. © 1979, American Chemical Society. All rights reserved.