text: A diphosphane linked with pentamethylene was claimed to span across a square planar complex. This early attempt was followed by ligands with more rigid backbones. "TRANSPHOS" was the first trans-spanning diphosphane ligand that usually coordinates to palladium(II) and platinum(II) in a trans manner. TRANSPHOS features [[Benzo(c)phenanthrene|benzo[c]phenanthrene]] substituted by diphenylphosphinomethyl (PhPCH) groups at the 1 and 11 positions. The polycyclic framework suffers sterically clashing hydrogen centers.