Metal Ions Control the Competition between β‐ and γ‐Hydrogen Transfer in the Generation of Propene from 1,7‐Octadiene in the Gas Phase

The mechanistic details (i.e. β‐versus γ‐hydrogen transfer) of transition‐metal ion induced generation of propene from metastable ion complexes of 1,7‐octadiene with M + =Cr + , Fe + , Ni + are strongly affected by the nature of M + . For Cr + the major reaction involves the transfer of an allylically activated hydrogen atom to M + (γ‐H transfer), followed by coupling of this hydrogen with the C 3 H 5 unit (Scheme 3: 8 → 9→ 11 → C 3 H 6 ). The hydrogen transfer 9→ 11 is preceded by substantial exchange reactions. A minor path for M + =Cr + corresponds to the more traditional β‐hydrogen transfer 9→ 10 . This process, however, represents the major route for propene loss induced by M + = Fe + , Ni + .