CARBON-TETRACHLORIDE THIOUREA (1/3) ADDUCT AT 170-K

CCl4.3CH4N2S, M(r) = 382.17, trigonal, R3BAR, a = 15.539 (4), c = 12.529 (9) angstrom, V = 2620.0 (20) angstrom 3, Z = 18, D(m) = 1.42 (2) (298 K), D(x) = 1.433 g cm-3 (170 K), lambda-(Mo K-alpha) = 0.71069 angstrom, mu = 10.17 cm-1, F(000) = 1164, T = 170 K, R = 0.043 for 640 observed (F > 6.0-sigma-F) reflections. The structure of the adduct has been solved and a model for the disordered carbon tetrachloride guest molecule has been developed. The adduct is isostructural with other non-aromatic adducts of this type. The carbon of the disordered carbon tetrachloride molecule is clearly co-planar with the three thiourea S atoms that point into the center of the thiourea channel. There appear to be Coulombic interactions between the partial negative charges on the three thiourea S atoms and the partial positive charge on the central C atom of the carbon tetrachloride guest molecule; these interactions seem to be the driving force involved in the formation of this adduct. A classification system for the various disorder types found in thiourea adducts has been developed and is introduced. Recognition of the disorder involved allowed the development of a reasonable model for the CCl4 molecule in the adduct.