The structure of dimeric 2,7-bis[4-(trifluoromethyl)phenyl]-4λ⁴,5λ⁴,9λ⁴,10λ⁴-tetrathieto[1,2-a:3,4-a′]bis [1,2,3,5]dithiadiazole (C₈H₄F₃N₂S₂)₂ and its adduct with triphenylstibine, (C₈H₄F₃N₂S₂)₂·C₁₈H₁₅Sb, both have triclinic (P) symmetry. They crystallize in layers containing centrosymmetric clusters consisting of four dithiadiazolyl dimers in the parent compound and two such dimers paired with two triphenylstibine units in the aromatic co-crystal. In the co-crystal, the Ph₃Sb molecules associate with an equivalent moiety from a neighbouring cluster in a geometry that is very reminiscent of other Ph₃Sb-containing structures. Thus, the adduct combines structural elements from those of its component parts. Key interactions between molecules in the pure dithiadiazolyl (S to S) and the co-crystal (S to C) are significantly shorter than the sums of atom van der Waals radii.