Abstract:The mixed valence europium nitridosilicate Eu 2 SiN 3 has been synthesized at 900°C in welded tantalum ampules starting from europium and silicon diimide Si(NH) 2 in a lithium flux. The structure of the black material has been determined by single-crystal X-ray diffraction analysis (Cmca (no. 64), a ) 542.3(11) pm, b ) 1061.0(2) pm, c ) 1162.9(2) pm, Z ) 8, 767 independent reflections, 37 parameters, R1 ) 0.017, wR2 ) 0.032). Eu 2 SiN 3 is a chain-type silicate comprising one-dimensional infinite nonbranched zweier chains of corner-sharing SiN 4 tetrahedra running parallel [100] with a maximum stretching factor f s ) 1.0. The compound is isostructural with Ca 2 PN 3 and Rb 2 TiO 3 , and it represents the first example of a nonbranched chain silicate in the class of nitridosilicates. There are two crystallographically distinct europium sites (at two different Wyckoff positions 8f) being occupied with Eu 2+ and Eu 3+ , respectively. 151 Eu Mö ssbauer spectroscopy of Eu 2 SiN 3 differentiates unequivocally these two europium atoms and confirms their equiatomic multiplicity, showing static mixed valence with a constant ratio of the Eu 2+ and Eu 3+ signals over the whole temperature range. The Eu 2+ site shows magnetic hyperfine field splitting at 4.2 K. Magnetic susceptibility measurements exhibit Curie-Weiss behavior above 24 K with an effective magnetic moment of 7.5 µ B /f.u. and a small contribution of Eu 3+ , in accordance with Eu 2+ and Eu 3+ in equiatomic ratio. Ferromagnetic ordering at unusually high temperature is detected at T C ) 24 K. DFT calculations of Eu 2 SiN 3 reveal a band gap of ∼0.2 eV, which is in agreement with the black color of the compound. Both DFT calculations and lattice energetic calculations (MAPLE) corroborate the assignment of two crystallographically independent Eu sites to Eu 2+ and Eu 3+ .

In broad daylight: The double-decker thiostannate [(RSn(IV))(4)S(6)] (1, R = CMe(2)CH(2)COMe) condenses to form [{(RSn(IV))(2)(mu-S)(2)}(3)Sn(III)(2)S(6)] (2; see picture). This mixed-valent complex, which formally contains both Sn(III) and Sn(IV) atoms as confirmed by Mössbauer spectroscopy and DFT calculations, forms by a complicated, concerted mechanism. Additionally, 2 provides six carbonyl groups for further derivatization.

By reaction of SnI(2), SnI(4), and crown ether (18-crown-6) in the ionic liquid [NMe(n-Bu)(3)][N(Tf)(2)], Sn(3)I(8) x 2 (18-crown-6) is obtained in the form of black, plate-shaped crystals and crystallizes with a monoclinic lattice symmetry. In detail, Sn(3)I(8) x 2 (18-crown-6) is constituted of trigonal-bipyramidal [SnI(5)](-)-anions and [Sn(2)I(3)(18-crown-6)(2)](+)-cations. The cation exhibits an endocyclical coordination of Sn(2+) by the crown ether. Both constituents are linked via long-ranging I-I contacts to form an infinite network. Besides crystal structure analysis, the mixed valence state of tin is evidenced by (119)Sn-Mössbauer spectroscopy.

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Im Tageslicht kondensiert das Doppeldecker‐artige Thiostannat [(RSnIV)4S6] (1, R=CMe2CH2COMe) zum gemischtvalenten Komplex [{(RSnIV)2(μ‐S)2}3SnIII2S6] (2, siehe Bild), der (formal) SnIII‐ neben SnIV‐Zentren enthält, wie durch Mößbauer‐Spektroskopie und DFT‐Rechnungen bestätigt wurde. 2 weist sechs funktionelle CO‐Gruppen für weitere Reaktionen an der Ligandenhülle auf, und die Bildung scheint über einen komplizierten konzertierten Mechanismus zu verlaufen.