Trans-spanning ligand

A wide variety of ligands that chelate in the cis fashion already exist, but very few can link opposite vertices on a coordination polyhedron.

A diphosphane linked with pentamethylene was claimed to span across a square planar complex.

TRANSPHOS features benzo[c]phenanthrene substituted by diphenylphosphinomethyl (Ph2PCH2) groups at the 1 and 11 positions.

TRANSDIP, based on a α-cyclodextrin, is the first ligand to give exclusively trans-spanned complexes, even with d8 metal ion halides.

[4] Xantphos is sometimes classified as a trans-spanning ligand, with less steric bulk compared to TRANSPHOS.