title: The stable diiron(2.5) complex ion [(NC)(5)Fe(mu-tz)Fe(CN)5](5-), tz = 1,2,4,5-tetrazine, and its neighboring oxidation states.
abstract: The conceptually simple mixed-valent diiron compound (NEt(4))(5)[(NC)(5)Fe(mu-tz)Fe(CN)(5)] with the 1,2,4,5-tetrazine (tz) bridging ligand was obtained as a thermally and air-stable material that displays large and highly variable electrochemical comproportionation constants between about 10(8) (in water) and 10(19.0) (in acetonitrile). Strong metal-metal interaction is also evident from spectroscopic results obtained for the solid and for the dissolved species. The rather intense intervalence charge-transfer band occurs around 2400 nm; infrared and Mössbauer spectra reveal the high spectroscopic symmetry of the system according to an (Fe(2.5))(2) formulation. DFT calculations on the [(NC)(5)Fe(mu-tz)Fe(CN)(5)](6-) ion confirm the presence of very low-lying pi(tz) and high-lying d(Fe) orbitals.
authors.affiliation: Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Glöckle
authors.forename: W
authors.initials: W
authors.lastname: Kaim
authors.forename: A
authors.initials: A
authors.lastname: Klein
authors.forename: E
authors.initials: E
authors.lastname: Roduner
authors.forename: G
authors.initials: G
authors.lastname: Hübner
authors.forename: S
authors.initials: S
authors.lastname: Zalis
authors.forename: J
authors.initials: J
authors.lastname: van Slageren
authors.forename: F
authors.initials: F
authors.lastname: Renz
authors.forename: P
authors.initials: P
authors.lastname: Gütlich