The structure of 6,7-pentaselena-1,4-diphosphabicyclo[2.2.1]heptane is
built from separate norbornane-like molecules with Se atoms in the br
idging position. The P-Se bond lengths fall in the range 2.234 (2)-2.2
54 (2) angstrom and the Se-Se bond lengths are 2.387 (1) and 2.390 (1)
angstrom.