The family of iron arsenide superconductors is expanded by the new iron platinum compounds (CaFe1−xPtxAs10)Pt4−yAs8 with novel crystal structures. Layers of FeAs4/4 tetrahedra and of nearly planar PtAs4/2 squares with (As2)4− dumbbells are stacked in different ways, resulting in polytypes with triclinic or tetragonal symmetry. Superconductivity up to 35 K is induced either by Pt doping of the Fe site or by electron transfer from PtAs to FeAs layers.

The alkaline earth diazenides M AE N 2 with M AE = Ca, Sr and Ba were synthesized by a novel synthetic approach, namely, a controlled decomposition of the corresponding azides in a multianvil press at highpressure/high-temperature conditions. The crystal structure of hitherto unknown calcium diazenide (space group I4/mmm (no. 139), a = 3.5747(6) Å, c = 5.9844(9) Å, Z = 2, wR p = 0.078) was solved and refined on the basis of powder X-ray diffraction data as well as that of SrN 2 and BaN 2 . Accordingly, CaN 2 is isotypic with SrN 2 (space group I4/mmm (no. 139), a = 3.8054(2) Å, c = 6.8961(4) Å, Z = 2, wR p = 0.057) and the corresponding alkaline earth acetylenides (M AE C 2 ) crystallizing in a tetragonally distorted NaCl structure type. In accordance with literature data, BaN 2 adopts a more distorted structure in space group C2/c (no. 15) with a = 7.1608(4) Å, b and their remarkable properties (e.g., superconductivity, photoluminescence, magnetism and low compressibility comparable to that of c-BN) 15−24 justify the investigation of the crystalline structure, stability, elasticity and electronic structures of the diazenides. However, except for M = Sr, Ba, Os, Ir, Pd and Pt, no other metal diazenides or pernitrides of formula type MN 2 have been synthesized in crystalline form as yet, but have been predicted by density-functional calculations to form under HP/HT conditions. 24−29 In order to extend the class of nitrogen rich metal diazenides or pernitrides, we have targeted new synthetic approaches for these compounds, and we were successful using controlled decomposition of highly reactive precursors like the corresponding azides. In this contribution, we present our novel synthesis route for the alkaline earth diazenides SrN 2 and BaN 2 . In addition, we report on the synthesis, structural, spectroscopic and electronic characterization of the novel alkaline earth diazenide CaN 2 and compare its structure to the predicted model. 26,29

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Dinitrogen (N2) ligation is a common and well-characterized structural motif in bioinorganic synthesis. In solid-state chemistry, on the other hand, homonuclear dinitrogen entities as structural building units proved existence only very recently. High-pressure/high-temperature (HP/HT) syntheses have afforded a number of binary diazenides and pernitrides with [N2](2–) and [N2](4–) ions, respectively. Here, we report on the HP/HT synthesis of the first ternary diazenide. Li2Ca3[N2]3 (space group Pmma, no. 51, a = 4.7747(1), b = 13.9792(4), c = 8.0718(4) Å, Z = 4, wRp = 0.08109) was synthesized by controlled thermal decomposition of a stoichiometric mixture of lithium azide and calcium azide in a multianvil device under a pressure of 9 GPa at 1023 K. Powder X-ray diffraction analysis reveals strongly elongated N–N bond lengths of dNN = 1.34(2)–1.35(3) Å exceeding those of previously known, binary diazenides. In fact, the refined N–N distances in Li2Ca3[N2]3 would rather suggest the presence of [N2](3·–) radical ions. Also, characteristic features of the N–N stretching vibration occur at lower wavenumbers (1260–1020 cm(–1)) than in the binary phases, and these assignments are supported by first-principles phonon calculations. Ultimately, the true character of the N2 entity in Li2Ca3[N2]3 is probed by a variety of complementary techniques, including electron diffraction, electron spin resonance spectroscopy (ESR), magnetic and electric conductivity measurements, as well as density-functional theory calculations (DFT). Unequivocally, the title compound is shown to be metallic containing diazenide [N2](2–) units according to the formula (Li(+))2(Ca(2+))3([N2](2–))3·(e(–))2.

We present a study of the structural and physical properties of directly hole doped LaFe 1-x Mn x AsO (x = 0.0-0.2) and the influence of charge compensation / electron-doping by additional F doping in LaFe 0.9 Mn 0.1 AsO 1-y F y (y = 0.1-0.5). High quality polycrystalline samples were prepared using a solid state metathesis reaction. The unit cell increases upon Mn doping, but decreases again when additional F is inserted. The semiconducting character of LaFe 1-x Mn x AsO decreases with additional F doping. Muon spin relaxation (µSR) measurements reveal short range magnetic order in LaFe 1-x Mn x AsO and a suppression of magnetism by additional electron-doping with fluoride in LaFe 0.9 Mn 0.1 AsO 1-y F y . Superconductivity remains absent even though the electronic preconditions are fulfilled in electron-doped LaFe 0.9 Mn 0.1 AsO 1-y F y at x > 0.1, which is suggestive of effective pair breaking by Mn in this system.