Thiophene and Selenophene Binding at a Pd 3 Cluster Site

We report the triply bridging coordination of thiophene and selenophene to a trinuclear metal cluster site. The triply bridging coordination of selenophene at a Pd 3 site forms a unique spiro‐type Pd 5 cluster. Furthermore, either thiophene or selenophene is accommodated stably at a Pd 3 site supported by a backside μ 3 ‐cyclooctatetraene ligand through the face‐capping μ 3 ‐coordination. The Pd 3 site supported by the cyclooctatetraene ligand showed higher binding affinity of benzene over thiophene, although a Pd 2 site strongly favors thiophene over benzene.