Reactivity Tuning by Ligand Effects: Gas‐Phase Reactions of Fe(C 6 H 6 )O + versus “Bare” FeO +

The presence of a benzene ligand in Fe(C 6 H 6 )O + (1) has a profound effect on the gas‐phase reactivity of FeO + . While the latter oxide is known to act as an efficient C‐H/C‐C bond‐activation reagent, the ligated species 1 is entirely unreactive in that respect. However, 1 serves as an excellent reagent for transferring oxygen to various olefins. In addition, it is demonstrated that the ligand substitution Fe‐(C 6 H 6 )O + + X → Fe(X)O + + 6 H 6 ) follows two principally different pathways. For X = C 6 D 6 and C 5 H 5 N the traditional direct substitution process with attack at the metal centre is operative. However, for X = olefins it is argued that the olefin will not initially attack the metal center; rather, the reaction commences by coordinating the olefin X to the oxygen atom of Fe 6 H 6 )O + . The resulting intermediate ( 6 H 6 )Fe(OX) + will then fall apart either to separated Fe(OX) + / 6 H 6 ) or to Fe( 6 H 6 ) + /OX, thus bringing about an epoxidation of the olefin rather than ketone formation.