title: Indefinitely stable iron(IV) cage complexes formed in water by air oxidation.
abstract: In nature, iron, the fourth most abundant element of the Earth's crust, occurs in its stable forms either as the native metal or in its compounds in the +2 or +3 (low-valent) oxidation states. High-valent iron (+4, +5, +6) compounds are not formed spontaneously at ambient conditions, and the ones obtained synthetically appear to be unstable in polar organic solvents, especially aqueous solutions, and this is what limits their studies and use. Here we describe unprecedented iron(IV) hexahydrazide clathrochelate complexes that are assembled in alkaline aqueous media from iron(III) salts, oxalodihydrazide and formaldehyde in the course of a metal-templated reaction accompanied by air oxidation. The complexes can exist indefinitely at ambient conditions without any sign of decomposition in water, nonaqueous solutions and in the solid state. We anticipate that our findings may open a way to aqueous solution and polynuclear high-valent iron chemistry that remains underexplored and presents an important challenge.
authors.affiliation: Department of Chemistry, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Street, 01601 Kiev, Ukraine.
authors.forename: Stefania
authors.initials: S
authors.lastname: Tomyn
authors.affiliation: Department of Chemistry, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Street, 01601 Kiev, Ukraine.|Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany.
authors.forename: Sergii I
authors.initials: SI
authors.lastname: Shylin
authors.affiliation: qLeap Center for Theoretical Chemistry, Department of Chemistry, University of Aarhus, DK-8000 Arhus C, Denmark.
authors.forename: Dmytro
authors.initials: D
authors.lastname: Bykov
authors.affiliation: Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany.
authors.forename: Vadim
authors.initials: V
authors.lastname: Ksenofontov
authors.affiliation: Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Gumienna-Kontecka
authors.affiliation: Department of Inorganic Chemistry, Technische Universität Dresden, Bergstraße 66, D-01069 Dresden, Germany.|V.I. Vernadskii Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine, 03680 Kiev, Ukraine.
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Bon
authors.affiliation: Department of Chemistry, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Street, 01601 Kiev, Ukraine.
authors.forename: Igor O
authors.identifier: 0000-0002-1092-8035
authors.initials: IO
authors.lastname: Fritsky