The reversible isomerization of syn-1 to anti-1 occurs without cleavage of metal-ligand bonds, as demonstrated through a [4 + 2] cycloaddition with trans-1,2-bis(trimethylsilyl)ethene as the dienophile, which led to the trapping of an ortho-quinodimethane intermediate. Further evidence comes from kinetic studies. Ring opening in 1 proceeds considerably more slowly than in the case of the non-complexed analogue, a finding that can be explained by entropy effects.