AbstractLabeling experiments provide evidence that the Fe1‐ and CO1‐mediated losses of H2and 2 H2from tetraline are extremely specific in that both reactions follow a clearsyn‐1,2‐elimination involving C(1)/C(2) and C(3)/C(4), respectively. In the course of the multi‐step reaction, the metal ions do not move from one side of the π‐surface to the other. Independent experiments confirm that the kinetic isotope effect (KIE) associated with the loss of the first H2molecule is indeed larger than the KIE for the elimination of the secon