AbstractThe crystal and molecular structure of 1,1,4,4‐tetraphenyl‐1,4‐diphosphoniacyclohexane dibromide has been determined by a single‐crystal, x‐ray diffraction study using diffractometer data. The compound crystallizes in the monoclinic space group P21/c with unit cell constants of a = 12.777(1), b = 26.180 (2), c = 16.283 (1) Å, and β = 91.18(1)°. The structure was solved by the heavy atom method with the 4176 independent and statistically significant structure factors refining to a value of R = 0.07. The diphosphonium ring is in the chair conformation with each phosphorus ion having an axial and equatorial phenyl ring attached. P‐C and C‐C bond lengths of 1.78 ± .03 Å and 1.53 ± .03 Å respectively agree well with the literature value