Interaction of diiodine with some tetra-substituted dithiooxamides. Crystal and molecular structure of bis(morpholinothiocarbonyl)bis(diiodine)

The reaction of some tetra-substituted dithiooxamides R 2 NC(S)C(S)NR 2 (R = CH 3 :Me 4 dto; R = C 2 H 5 :Et 4 dto; R 2 N = OC 4 H 8 N:Mo 2 dto) with diiodine has been investigated by spectrophotometric methods in CHCl 3 . The formation in solution of 1:1 and 1:2 charge-transfer (c.t.) complexes between the reagents has been observed. A new computer program, derived from "SUPERQUAD" (P. Gans, A. Sabatini, and A. Vacca. J. Chem. Soc. Dalton Trans. 1195 (1985)), has been applied to evaluate the formation constants. The 1:2 c.t. complexes have been isolated in the solid state, and an X-ray structure analysis of the [OC 4 H 8 NC(S)C(S)NC 4 H 8 O]*2I 2 compound indicated that the crystals are triclinic, space groups , with a = 14.659(6), b = 15.111(6), c = 9.317(5) Å, α = 92.29(2), β = 99.71(2), γ = 99.48(2)° and Z = 4. In particular the torsion angle SCCS (≈90°) shows that the conformation of the dithiooxamide is not trans.