The first example of a tetrahalogenated derivative of a diphosphadithiatetrazocine, 1,5-Cl2P(NSN)(2)PCl2 (3), was synthesized by cyclocondensation of a 2:1 mixture of SCl2 and SO2Cl2 with Cl2P(NSiMe3)N(SiMe3)(2) in CH2Cl2. The heterocycle 3 was isolated as an orange, moisture-sensitive, thermally labile solid and characterized by mass spectrometry, P-31 NMR, and UV visible spectroscopy, The low-field P-31 NMR chemical shift (93.7 ppm) is indicative of a cross-ring S-S interaction in the eight-membered P2N4S2 ring, and this conclusion is supported by densityfunctional computations. Compound 3 exhibits unusual physical properties compared with those of the known tetraalkyl or aryl derivatives; mild heating (90 degrees C) produces an orange rubbery material. The bishomoaromatic character of the diphosphadithiatetrazocine 1,5-R2P(NSN)(2)PR2 (R = Me, Cl, F) is evinced by the negative nucleusindependent chemical shift (NICS) values, and the through-space bishomoconjugation in the eight-membered ring decreases with increasing electronegativity of the substituents attached to the P atoms.