Isomerism in some 1-oxa-3,5-dithians and the X-ray structure determination of 2,6-bis(trichloromethyl)-4-dichloromethylene-1-oxa-3,5-dithian

Abstract

2,6-bis (trichloromethyl)-4-dichloromethylene-1-oxa-3,5-dithian is triclinic,P¯1,a=10.125(3),b=10.294(3),c=14.631(10) A,α=92.84(5),β=96.51(5), γ=96.18(2)°,V=1503 A3,Z=4. The structure was solved by direct methods, from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by least squares to a finalR value of 0.035 using 3961 reflections. The conformation of the molecules is twist-boat, one molecule being almost symmetrically twisted about the O-C(Cl2) direction. The range of endocyclic O-C-S angles is 111.8(3) to 115.1(3)° and data are given which support the possibility of there being a correlation between the endocyclic O-C(X)-S angle, the C-O-C(X)-C(Cl3) torsion angle, and the C-S-C(X)-C(Cl3) torsion angle. The -CCl3 groups are in pseudoequatorial positions. Average bond lengths (A) for the two molecules are C-O 1.405, C(sp3)-S 1.822, C(sp2)-S 1.759, C-Ceq 1.529 and average endocyclic angles (°) are O 117.3, C (sp3) 113.5, S 97.4, C(sp2) 119.3, the esds on the individual bond lengths and angles being in the ranges of 0.003–0.004 A and 0.2–0.4° respectively.