Definitive Proof for the Operation of Isotopically Sensitive Branching (‘Metabolic Switching’) in Fe I ‐Mediated CH Bond Activation in the Gas Phase Short Communication

Rigorous regio‐ and stereospecific labeling experiments are performed to demonstrate the operation of the previously suggested operation of ‘isotopically sensitive branching’ in Fe I ‐mediated CH bond activation. For the hexane‐1,6‐diol/Fe + ‐complex, it is shown that dehydrogenation involves specifically the central C(3)/C(4) position, and the study of the stereospecifically labeled D , L ‐ and meso‐[3,4‐D 2 ]‐isotompomers 1e and 1f demonstrates that dehydrogenation proceedes via two competing pathways ( i.e. ‘anti’‐ vs. ‘syn ’‐route). The contribution of these routes to the product formation is – due to a kinetic isotope effect – controlled by the relative configuration at the labeled positions C(3)/C(4) . For the D , L ‐form 1e , we estimate a ratio of 49:1 in favor of the ‘ anti ’‐route; due to an isotope effect, this ratio drops to 4.3:1 for the meso ‐form 1f .