The Stable Diiron(2.5) Complex Ion [(NC)₅Fe(μ-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.

(Pr4N)4[Ag3Fe2(ECN)12]—Anionic Network Structures with Mutual Interpenetration

“…[15] These complexes can be assigned to class II in the sense of the Robin Day classification [20] with localized oxidation states, since the n CN frequencies for the Fe II (CN) 5 and Fe 5À (m-tz = 1,2,4,5-tetrazine), however, cannot be distinguished by either IR or Mössbauer spectroscopy, and can therefore be assigned to class III, which is also supported by a minor solvent dependence of the significantly sharper intervalence charge-transfer band at 2495 cm À1 . [21] Because in 1 the Fe 2+ and the Fe 3+ ions have similar chemical environments, the magnetic features correspond to those of the isolated complexes, and these ions also give rise to distinct signals in the Mössbauer spectra, 1 should be considered a Robin Day class II mixed-valent compound.…”

Molecular switching in iron complexes bridged via tin-cyanides observed by Mössbauer and ESR spectroscopy

“…Our systematic approach [2][3][4][5][6][7][8][9][10][11][12][13] enabled us to apply chemical tuning on pentadentate ligand Fe(III) complexes as building units [LFe III -X] (L= bis(3-salicylidene aminopropyl) amine) and show multistability, e.g. multiple thermally induced transitions between low-spin (LS) 2 T(O h ) and high-spin (HS) 6 A(O h ) in various star-shaped compounds: tetranuclear [4], heptanuclear [3,5,6,7,8,9], nonanuclear [2,3,6,7,8,9], and dodecanuclear [10].…”

Chemical tuning by 5-Methyl and N-Methyl-substitution in heptanuclear complexes effects multistability investigated by Mössbauer spectroscopy

“…Along that line our synthetic approach is to perform systematic derivatisation, e.g. the pentadentate ligand LH 2 and its complexes [Fe (III) ( N−R− L)X] (LH 2 =bis(3-salicylidene aminopropyl) amine) combined to multinuclear compounds [1][2][3][4][5][6][7][8][9][10][11][12]. Recently, we achieved unprecedented molecular switches with multistability, e.g.…”