アイテム詳細

要旨

The Fe^III azide complexes [Fe^III (N₃ )cyclam-ac]PF₆ (1⋅PF₆ ), [Fe^III (N₃ )Me₃ cyclam-ac]PF₆ (2⋅PF₆ ), and trans-[Fe^III (N₃ )₂ cyclam]ClO₄ (3⋅ClO₄ ) (cyclam=1,4,8,11-tetraazacyclotetradecane; cyclam-ac=1,4,8,11-tetraazacyclotetradecane-1-acetate; Me₃ cyclam-ac=4,8,11-trimethyl-1,4,8,11-tetraazacyclotetra-decane-1-acetate) are studied in the gas phase with special emphasis on the formation of high-valent iron nitrides by collision-induced dissociation. Whereas the azide complex with unsubstituted cyclam-acetate 1 as major fragmentation expels N₂ to form a high-valent Fe^V nitride complex, a similar process is not observed for its methyl-substituted congener. In contrast, loss of an azide radical results in iron reduction to Fe^II . Thus, the gas-phase behavior is parallel to the results obtained in spectroscopic studies of photolyzed frozen solution. The diazide complex 3 mainly fragments via consecutive losses of HN₃ without change in the iron oxidation state. However, small amounts of dinitrogen loss and thus Fe^V nitride formation are also observed. While it is assumed that the Fe^V nitride complex detected by Mössbauer spectroscopy in frozen solution is still coordinated by an azide in the trans position to the nitride, both the complex [Fe^V (N)(N₃ )(cyclam)]⁺ still bearing an intact second azide and the coordinatively unsaturated [Fe^V (N)(cyclam-H)]⁺ are observed in the gas phase.