Bond stretch isomerism is confirmed for complexes subject to
spin crossover transitions. In some octahedral complexes of d6 configuration, the depopulation of eg orbitals causes significant contractions of the metal-ligand bond distances. The phenomenon is mainly manifested in the solid forms of the compounds. File:Fe(picNH2)3.png|thumb|center|400 px|Light-induced spin-crossover of [Fe(pyCH2NH2)3]2+, which switches from high and low-spin. Although no example of bond stretch isomerism has been established in solution, two isomers have been crystallized for
pentamethylcyclopentadienyl ruthenium dichloride dimer ([Cp*RuCl2]2). One has an Ru-Ru bond (2.93 Å) and the other has a long intermetallic distance of 3.75 Å. The former isomer is thought to be diamagnetic, and the latter is magnetic. ==References==