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Exceptionally electron‐rich, nearly trigonal‐planar tricyanidometalate anions [Fe(CN)3]7− and [Ru(CN)3]7− were stabilized in LiSr3[Fe(CN)3] and AE3.5[M(CN)3] (AE=Sr, Ba; M=Fe, Ru). They are the first examples of group 8 elements with the oxidation state of −IV. Microcrystalline powders were obtained by a solid‐state route, single crystals from alkali metal flux. While LiSr3[Fe(CN)3] crystallizes in P63/m, the polar space group P63 with three‐fold cell volume for AE3.5[M(CN)3] is confirmed by second harmonic generation. X‐ray diffraction, IR and Raman spectroscopy reveal longer C−N distances (124–128 pm) and much lower stretching frequencies (1484–1634 cm−1) than in classical cyanidometalates. Weak C−N bonds in combination with strong M−C π‐bonding is a scheme also known for carbonylmetalates. Instead of the formal notation [Fe−IV(CN−)3]7−, quantum chemical calculations reveal non‐innocent intermediate‐valent CN1.67− ligands and a closed‐shell d10 configuration for Fe, that is, Fe2−., The electron‐rich cyanidometalates [Fe(CN)3]7− and [Ru(CN)3]7− represent the first examples of group 8 elements with an oxidation state of −IV. DFT calculations reveal a nominal d10s0 configuration, which corresponds to an effective charge of 2−. The high negative charge also weakens the C−N bonds by the population of antibonding states.

The first nitridogermanates(III) Ca6 [Ge2 N6 ] and Sr6 [Ge2 N6 ] were synthesized from sodium flux and structurally characterized by powder and single crystal X-ray diffraction, respectively. They crystallize isostructurally to each other and homeotypic to Ca6 [Cr2 N6 ]H in space group R 3‾ . They feature unprecedented, mutually isolated, ethane-like [GeIII2 N6 ]12- anions in a staggered conformation. The compounds are semiconductors according to resistivity measurements and electronic structure calculations, yielding band gaps of 1.1 eV for Ca6 [Ge2 N6 ] and 0.2 eV for Sr6 [Ge2 N6 ].

${\mathrm{Li}}_{2}\mathrm{Sr}{[\mathrm{MnN}]}_{2}$ single crystals were successfully grown out of Li-rich flux. The crystal structure was determined by single-crystal x-ray diffraction and revealed almost linear $\ensuremath{-}\mathrm{N}\ensuremath{-}\mathrm{Mn}\ensuremath{-}\mathrm{N}\ensuremath{-}\mathrm{Mn}\ensuremath{-}$ chains as central structural motif. Tetragonal blocks of air and moisture-sensitive nitridomanganate were employed for electrical transport, heat capacity, and anisotropic magnetization measurements. Both the electronic and magnetic properties are most remarkable, in particular the linear increase of the magnetic susceptibility with temperature that is reminiscent of underdoped cuprate and Fe-based superconductors. Clear indications for antiferromagnetic ordering at ${T}_{N}=290$ K were obtained. Metallic transport behavior is experimentally observed in accordance with electronic band structure calculations.

Two new calcium nitridomanganates, Ca12 [Mn19 N23 ] (P3, a=11.81341(3) A, c=5.58975(2) A, Z=1) and Ca133 [Mn216 N260 ] (P3‾ , a=39.477(1) A, c=5.5974(2) A, Z=1), were obtained by a gas-solid reaction of Ca3 N2 and Mn with N2 at 1273 K and 1223 K, respectively. The crystal structure of Ca12 [Mn19 N23 ] was determined from high-resolution X-ray synchrotron powder diffraction data, whereas single-crystal X-ray diffraction was employed to establish the crystal structure of the Ca133 [Mn216 N260 ] phase, which classifies as a complex metallic alloy (CMA). Both crystal structures have 2D nitridomanganate layers containing similar building blocks but of different levels of structural complexity. Bonding analysis as well as magnetic susceptibility and electron spin resonance measurements revealed that only a fraction of the Mn atoms in both structures carries a localized magnetic moment, while for most Mn species the magnetism is quenched as a result of metal-metal bond formation.

Single crystals of the compounds Li2 AeTt (Ae=Ca, Ba, Tt=Si, Ge, Sn, Pb) were grown in reactive lithium melts in sealed tantalum ampoules from an equimolar ratio of the alkaline earth metal and the respective group 4 element. All compounds, with the exception of Li2CaSn and Li2CaPb, are isotypic and crystallize in an orthorhombic unit cell (space group Pmmn, no. 59). The crystal structure can be characterized as superimposed corrugated networks of Li2 Tt connected by calcium or barium atoms within the third dimension. Li2CaSn and Li2CaPb crystallize in the cubic space group Fm3̅m (no. 225) in a Heusler-type (MnCu2Al) structure. According to magnetic susceptibility and electric resistivity measurements, the compounds Li2BaGe, Li2BaSn, and Li2BaPb represent diamagnetic activated semiconductors.

Large single crystals of Li2(Ca3N)2[Ga4] and Li2(Sr3N)2[Ga4] up to several mm in size were grown from mixtures of the respective elements and binary alkaline-earth metal nitrides in reactive lithium melts employing a modified high-temperature centrifugation-aided filtration (HTCAF) technique. The main structural features of these isotypic phases are stella quadrangula building units [Ga4]Li4/2 and octahedra (Nae6/2), which form two independent interpenetrating networks. The phases crystallize in the η-carbide structure and represent diamagnetic small bandgap semiconductors. Real-space chemical bonding analysis indicates predominantly ionic bonding.

The unprecedented, fully deprotonated form of acetonitrile, the acetonitriletriide anion CCN3−, is experimentally realized for the first time in the stabilizing bulk host framework of the Ba5[TaN4][C2N] nitridometalate via a one-pot synthesis from the elements under moderate conditions (920 K). The molecular structure of this long-sought acetonitrile derivative is confirmed by X-ray diffraction, as well as NMR, IR, and Raman spectroscopy. The anion is isoelectronic to the CO2 molecule, and, in contrast to acetonitrile (H3C−C≡N), the electron pairs are shifted towards two double bonds, that is, [C=C=N]3−.

The title compound Ca_3[BN_2]I_3 was obtained from reactions of mixtures of the starting materials Ca_3[BN_2]_2 and CaI_2 in a 1:4 ratio in sealed Nb tubes at 1223 K. The crystal structure was solved from powder synchrotron diffraction data. Ca_3[BN_2]I_3 is the first example of a halide-rich nitridoborate crystallizing in the rhombohedral space group R32 [no. 155, Pearson code: hR96; Z = 12; a = 16.70491(2) A, c = 12.41024(2) A]. The crystal structure is built up by two interpenetrating networks of condensed edge-sharing [BN_2]@Ca_6 and [□]@I_6 trigonal antiprisms (□ = void). In Ca_3[BN_2]I_3 two crystallograhically distinct [BN_2]^(3–) anions are present with d(B1–N) = 1.393(2) A and d(B2–N) = 1.369(9) A. Their bond angles are practically linear, varying only slightly: N–B1–N = 179(1)° and N–B2–N = 180°. Vibrational spectra were interpreted based on the D_(∞h) symmetry of the discrete linear [N–B–N]^(3–) moieties, considering the site symmetry reduction and the presence of two distinct [BN_2]^(3–) groups.

Brownish gray microcrystalline powders of Ba3[Rh(CN)3] were synthesized from pellets of mixtures of Ba2N, rhodium, NaCN, and graphite at 1070 K in an argon atmosphere. Synchrotron powder diffraction data at 293(1) K revealed the crystal structure of the compound [P63/m, a = 9.23266(7) A, c = 5.81612(6) A] is isostructural to Ba3[Co(CN)3] and Ba3[Ir(CN)3]. The trigonal-planar complex [Rh(CN)3]6– is surrounded by nine Ba2+ cations forming a tri-capped trigonal prism. Compared to typical cyano ligands, the C–N bond is long [1.21(5) A] and the vibrational frequencies are low (IR 1674 cm–1, Raman 1728 cm–1).

Na3[BN2] and Na2K[BN2] were obtained as white polycrystalline powders from the reaction of the respective binary mixtures NaNH2:NaBH4 and NaNH2:KBH4 in molar ratio 2:1 at 873 K and 683 K, respectively, in an argon stream. According to the results of thermal analysis measurements, both compounds are thermally stable only up to 954 K (Na3[BN2]) and 712 K (Na2K[BN2]), respectively, decomposing under evolution of alkali metal and nitrogen to yield hexagonal BN as final residue, which was identified from powder patterns. The crystal structure of Na3[BN2] {β-Li3[BN2] type; P21/c (No. 14); Z = 4} was confirmed and the unit cell parameters redetermined: a = 5.724(1) A, b = 7.944(1) A, c = 7.893(1) A, β = 111.31(1)°. According to X-ray powder data, Na2K[BN2] crystallizes isotypic to Na2KCuO2 in the tetragonal space group I4/mmm (No. 139) with a = 4.2359(1) A, c = 10.3014(2) A and Z = 2. The crystal structure of Na2K[BN2] is composed of linear [N–B–N]3– anions centering elongated M14 rhombic dodecahedra, which are formed by 8 sodium and 6 potassium atoms. The [BN2]@Na8/4K6/6 polyhedra are stacked along [001] and condensed via common tetragonal faces to generate a space-filling 3D arrangement. The B–N bond lengths for the strictly linear [N–B–N]3– units are 1.357(4) A. Vibrational spectra of the title compounds were measured and analyzed based on D∞h symmetry of the relevant [N–B–N]3– groups taking into account the site symmetry effects for Na3[BN2]. Both the wavenumbers, as well as the calculated valence force constants f(B–N) = 7.29 N·cm–1 (Na3[BN2]) and 7.33 N·cm–1 (Na2K[BN2]), respectively, are in good agreement with those of the known alkali and alkaline earth dinitridoborates.

Mg2[BN2]Br was prepared from stoichiometric mixtures of the respective binary components Mg3N2, MgBr2 and BN in sealed niobium ampoules placed in evacuated silica tubes at 1473 K. The monoclinic crystal structure (C2/c (no. 15); a = 9.1509(3) A, b = 6.6209(3) A, c = 6.4756(2) A, β = 109.353(3)° and Z = 4) was determined from powder data. The crystal structure is characterized by cationic 32.4.3.4 nets of magnesium and anionic hexagonal closed packed 36 nets of six-connected nodes occupied by [N–B–N]3– units and Br– anions. Both types of planar nets alternate along the [100] direction. The packing of such incoherent nets results in a monoclinic symmetry, which is a compromise for a structure built up from rod-like [N–B–N]3– units and spherical bromine and magnesium atoms. Bond length and bond angle for the [N–B–N]3– unit are d(B–N) = 1.354(2) A and ∠(N–B–N) = 177.1(9)°, respectively., Vibrational spectra were analyzed based on the D∞h symmetry of the relevant [N–B–N]3– moieties, considering the site symmetry splitting. The results are discussed in context with those of the known members of the magnesium dinitridoborate halide series, Mg2[BN2]Cl and Mg8[BN2]5I.

The transparent dark orange compounds Cs2[Pd(N3)4] and Rb2[Pd(N3)4]·2/3H2O are synthesized by reaction of the respective binary alkali metal azides with K2PdCl4 in aqueous solutions. According to single-crystal X-ray diffraction investigations, the novel ternary azidopalladates(II) crystallize in the monoclinic space group P21/c (no. 14) with a = 705.7(2) pm, b = 717.3(2) pm, c = 1125.2(5) pm, β = 104.58(2)°, mP30 for Cs2[Pd(N3)4] and a = 1041.4(1) pm, b = 1292.9(2) pm, c = 1198.7(1) pm, β = 91.93(1)°, mP102 for Rb2[Pd(N3)4]·2/3H2O, respectively. Predominant structural features of both compounds are discrete [PdII(N3)4]2– anions with palladium in a planar coordination by nitrogen, but differing in point group symmetries., The vibrational spectra of the compounds are analyzed based on the idealized point group C4h of the spectroscopically relevant unit, [Pd(N3)4]2– taking into account the site symmetry splitting due to the symmetry reduction in the solid phase.

Sr6[CoN2]2[CN2] was prepared from Sr2N, carbon, cobalt, and NaN3 as nitrogen source. The crystal structure (I4/mmm (no. 139), a = 383.55(10) pm, c = 1237.8(4) pm) represents a Na2[HgO2] type arrangement with both linear [CoIN2]5– and smaller [CN2]2– ions mutually occupying the [HgO2] position.

The title compound Na2[BH4][NH2]≡Na2BNH6 exists in two different modifications: the low-temperature (LT) β- and the high-temperature (HT) α-phase. The HT α-Na2BNH6 is accessible by single heating of the binaries NaNH2 and NaBH4 (molar ratio = 1:1) to the melting point of 492 K for 1 h in evacuated Pyrex ampoules. On longer annealing (T = 342 K, 10 days), the HT α-phase converts completely to the LT β-phase. The β → α transition at 371 K is very fast, but the conversion α → β is quite slow. No further phase formation was detected in the system up to a molar ratio of 5:1 (NaNH2:NaBH4). The cubic α-Na2BNH6 crystallizes in the K3SO4F-type of structure (space group: P m 3 ¯ m , Z = 1) with a = 4.6950(1) A. β-Na2BNH6 crystallizes in orthorhombic symmetry (space group: Pbcm, Z = 4) with a = 6.5384(2) A, b = 6.4960(1) A, c = 9.8512(2) A. Both structures can directly be derived from the perovskite type structure ABO3, with the [BH4]− and [NH2]− moieties in the A and B sites, respectively. The charge balancing Na ions are occupying 2/3 of the O positions. In both cases, the presence of the two different anions in the solids was also confirmed by vibrational spectra. According to DTA and high temperature X-ray diffraction (HT-XRD) measurements, the educts NaNH2 and NaBH4 react at 430 K to form α-Na2BNH6 which remains stable until the melting point of 492 K. Between 492 and 573 K, no significant effects were detected in DTA and TG. Above 573 K, however, a sudden decomposition takes place in two steps (659 and 689 K) causing a total mass loss of 8%. The gaseous species formed during the decomposition process were followed by mass spectra (MS). The mass spectra obtained from 1:1 and 2:1 mixtures of NaNH2 and NaBH4 in the range 492 K The vibrational spectra of the title compounds Na2BNH6 have been measured and interpreted based on the Td and C2v symmetry of the relevant [BH4]− and [NH2]− groups. Both the (N–H) and (B–H) frequencies exhibit small but significant shifts with respect to the pure binaries.

The first nitridocobaltate carbodiimide (Sr6N)[CoN2][CN2]2 has been synthesized from the elements Sr, Co, and graphite powder and NaN3 (as a nitrogen source). The crystal structure was determined from X-ray single-crystal diffraction data as orthorhombic (space group P21212, No. 18, a=9.8807(6) A, b=14.6474(9) A, c=3.8569(3) A, V=558.2 A3, Z=2, R1=0.0265, wR2=0.0383). (Sr6N)[CoN2][CN2]2 is the first low-valency 3d-transition nitridometalate containing additional [CN2]2− groups. The crystal structure can be described as an array of rocksalt-like columns of Sr and N linked via common corners and connected by [N=C=N]2− and [CoIN2]5− units located within structural channels running along [0 0 1]. The magnetic susceptibility follows the Curie–Weiss law with an effective moment of 3.26 μB consistent with two unpaired spins (d8, CoI). The compound is a bad metallic conductor with a resistivity of order 1 mΩ cm at 300 K. Vibrational spectroscopic data support the existence of carbodiimide [N=C=N]2− species. The Co K-edge X-ray absorption spectra (XAS) of Ca5[CoN2]2 and (Sr6N)[CoN2][CN2]2 confirm the presence of CoI within the complex anions.

Ca5N5V, orthorhombic, Pbcm (no. 57), a = 6.0371(3) Å, b = 16.6146(7) Å, c = 6.7815(3) Å, V = 680.21(5) Å3, Z = 4, R(P) = 0.0100, RF(all) = 0.0348, T = 293 K.

The formation of ternary nitridometalates from the elements in the case of the systems Li—Cr, V, Mn—N leads to compounds which contain the transition metals in the highest (VV, CrVI) or a comparably high (MnV) oxidation state. In the corresponding calcium and strontium systems, the transition metals show a lower oxidation state (VIII, CrIII, MnIII). Transition metals with intermediate oxidation states (CrV, MnIV) are present in the quaternary (mixed cation) compounds Li4Sr2[CrN6], Li6Ca2[MnN6], and Li6Sr2[MnN6] (R3¯(#148), a = 585.9(3) pm, c = 1908.6(4) pm, Z = 3), as well as in the solid solution series Li6(Ca1—xSrx)2[MnN6]. Zur Kontrolle der Oxidationsstufen von Ubergangsmetallen (Cr, Mn) in Nitridometallaten und zur Kenntnis der Mischkristallreihe Li6(Ca1-xSrx)[Mn2N6] Bei der Darstellung aus den Elementen liegt in ternaren Nitridometallaten des Vanadiums, Chroms und Mangans das Ubergangsmetall in den Lithiumverbindungen in der hochstmoglichen (VV, CrVI) oder einer hohen Oxidationsstufe (MnV) vor, in den entsprechenden Calcium- und Strontium-Verbindungen in einer niedrigeren (VIII, CrIII, MnIII). In den quaternaren Verbindungen Li4Sr2[CrN6], Li6Ca2[MnN6] und Li6Sr2[MnN6] (R3¯(#148), a = 585.9(3) pm, c = 1908.6(4) pm, Z = 3) sowie der Mischkristallreihe Li6(Ca1—xSrx)2[MnN6] weist das Ubergangsmetall dagegen eine mittlere Oxidationsstufe auf (CrV, MnIV).

Greenish gray microcrystalline powders of Ba3[Ir(CN)3] were prepared from pressed pellets of mixtures of Ba2N, iridium, NaCN, and graphite at 1020 K under inert conditions. Neutron diffraction data at 293 K revealed the crystal structure of the Ir compound (P63/m (no. 176), a = 9.2277(8) A, c = 5.7878(6) A) to be isostructural to Sr3[Co(CN)3] and Ba3[Co(CN)3]. The trigonal-planar complex [Ir3(CN)3]6– is surrounded by nine Ba2+ ions forming a tricapped trigonal prism. Elongated C–N distances and low vibrational frequencies in the highly reduced iridium complex are similar to those observed in the corresponding cobalt compounds.

Sr5[NbN4]N (transparent, red single crystals) was synthesized by reaction of Sr2N with Nb under nitrogen at ambient pressure and 1223 K. The crystal structure was solved and refined in the space group Pbcm (no. 57), Z = 4, with lattice constants a = 646.6(3) pm, b = 1792.5(9) pm, c = 729.8(4) pm, and R = 0.019, wR2 = 0.034. The crystal structure contains both isolated tetrahedra [NbN4]7- as well as chains of corner sharing octahedra 1(Sr4Sr2/2N7+). Strontium is irregularly coordinated by nitrogen (CN = 4 - 6, Sr-N: 252.3(4) - 340.8(3) pm); nitrogen is located in a distorted octahedral environment by strontium and niobium (Nb-N: 194.5(4) - 199.2(2) pm). By formal reduction of the structural building units to their centers a close structural relationship to both the NiAs and the CaSi type structure is evident.

The reinvestigation of the binary system Ba-Ni revealed the existence of Ba2Ni3 in the temperature range 450 °C–800 °C. Single crystals were grown at 700 °C in the presence of excess barium, followed by separation from the melt by use of the high-temperature centrifugation aided filtration technique, HTCAF. At ambient temperature Ba2Ni3 is in a metastable state which slowly transforms to the elements (side-phases of the binary system). The extreme softness and the mechanical instability of the hygroscopic Ba2Ni3 particles prevented a single crystal structure determination. The crystal structure was solved from X-ray powder diffraction data (Pm1 (No. 164), a = 419.97(2) pm, c = 913.32(3) pm) and revealed Ba2Ni3 to be an isotype of Sr2Ni3 which was reported only recently.

The members Ca 5 [CoN 2 ] 2 , Sr 5 [CoN 2 ] 2 and BaCa 4 [CoN 2 ] 2 of the novel isotypic nitridocobaltate series AE 5 [CoN 2 ] 2 ( P 4/ ncc ) containing linear [Co I N 2 ] 5− complexes were synthesized via high-temperature route. On addition of carbon to the reaction mixtures the nitridocobaltate(I) carbodiimides (Sr 6 N)[Co I N 2 ][CN 2 ] 2 ( P 2 1 2 1 2), and Sr 2 [Co I N 2 ] 1− x [CN 2 ] x ( x = 0.27) ≈ Sr 6 [Co I N 2 ] 2 [CN 2 ] ( I 4/ mmm ) are formed. The low-valence states of Co are investigated in detail. X-ray absorption spectroscopy (XAS) data confirm the assigned low oxidation states for Co in all the compounds under consideration. At high temperatures the nitridocobaltates reveal Curie–Weiss paramagnetic behaviour consistent with Co I and d 8 configuration ( S = 1). Electronic structure calculations and magnetic susceptibility data indicate antiferromagnetic interactions in Ca 5 [CoN 2 ] 2 and BaCa 4 [CoN 2 ] 2 .

Yellow single crystals of the isotypic phases Ca51[WN4]12N8O3 and Sr51[WN4] 12N8O3 (triclinic, P1̄ (#2 ); a= 1056.4(3) / 1113.1(5) pm, b = 1239.7(3) / 1304.4(5) pm, c= 1598.2(3) / 1679.4(9) pm, α = 102.78(1)/102.47(2)°, β= 95.15( 1)/95.43(3)°, γ = 109.89(1)/109.77(2)°; Z = 1) were grown in a Tl-flux (Ca:Tl, molar ratio 5:1, W-crucible; Tmax = 1273K; reaction with N2, 1 atm, 36 h) or from pellets (Sr2N + W, molar ratio 6:1; Tmax = 1023K; reaction with N2, 1 atm, 36 h). The crystal structures contain tetrahedral anions [WN4]6- in addition to isolated nitride and isolated oxide ions, which are octahedrally coordinated by Ca and Sr, respectively.

The crystal structure of a new potassium tantalum(V) cyclotetrasilicate, KTaSi{sub 2}O{sub 2} (K{sub 2}Ta{sub 2}Si{sub 4}O{sub 14}), has been determined by single crystal X-ray diffraction. KTaSi{sub 2}O{sub 7} crystallizes in the tetragonal system, space group P4/mbm with {alpha} = 8.735(2) and c= 7.999(2) {Angstrom}, V= 610.3(2) {Angstrom}{sup 3}, Z = 4, d{sub x} = 4.225 g/cm{sup 3}, {lambda} (MoK{alpha}) = 0.71073 {Angstrom}, {mu} = 190.7 cm{sup {minus}1}, F{sup {prime}} (000) = 704, T = 293 K, R = 0.0421, R{sub w} = 0.0789 for 451 unique reflections (R{sub int} = 0.0227) with F{sub O}{sup 2} > O. The framework structure of KTaSi{sub 2}O{sub 7} is built up from chains of corner-sharing TaO{sub 6} octahedra running parallel to the fourfold axes and linked together by four-membered Si{sub 4}O{sub 12} single units. AC impedance measurements on KTaSi{sub 2}O{sub 7} indicate low ionic conductivities, 5.6 x 10{sup {minus}9} and 3.0 x 10{sup {minus}7} {Omega} {center_dot} cm{sup {minus}1} at 333 and 546{degrees}C, respectively. An activation energy of 0.83 {plus_minus} 0.02 eV is observed.

Black crystals of the isotypic phases LiBa4[Mo2N7] and LiBa4[W2N7] (monoclinic, P2/n; a = 1552.2(3)/1555.2(4), b = 642.2(1)/644.4(1), c = 1039.9(2)/1042.4(2) pm; β = 99.23(2)/99.30(3)°; Z = 4) were grown from the melt (Li, Ba3N2, Mo/W; molar ratio 20 : 5 : 1;Tmax = 1323 K; reaction with N2, 1 atm, 18 h) by cooling (20 K/h). The crystal structures contain two independent dimeric units [ MO2N7]9- / [W2N7]9- (staggered conformation; Mo/W -N -Mo/W : 173.6/173.7° and 180°/180°; Mo/W -N(term): 180(2)-185(1)/181(3)-185(1) pm; Mo/W -N(bridg) : 195(1)/194(1) pm and 193(1)/194(1) pm).

Co2N4Sr5, tetragonal, P4/ncc (no. 130), a = 8.6730(5) Å, c = 12.443(1) Å, V = 936.0 Å3, Z = 4, Rgt(F) = 0.0293, wRref(F2) = 0.0684, T = 295 K.

The title compounds Sr-2[BN2]Br (1), Eu-2[BN2]Br (2) and Eu-2[BN2]I (3) were obtained from reactions of mixtures of Sr-3[BN2](2) and SrBr2 (1) and the binaries EuN, h-BN and EuX2 (X = Br, I) (2, 3), respectively. The crystal structure of Sr-2[BN2]Br was solved from X-ray powder diffraction data and those of the europium compounds from X-ray single crystal data. Sr-2[BN2]Br and Eu-2[BN2]Br are isotypic crystallizing in the rhombohedral space group R (3) over barm (No. 166, Pearson code: hR18; Z = 3; a = 4.11692(2) angstrom, c = 26.4611(2) angstrom (1); a = 4.0728(3) angstrom, c = 26.589(3) angstrom (2)). The crystal structures are built up by layers of condensed edge-sharing [B-N-B]@Eu-6 and [Br]@Eu-6 trigonal antiprisms, which are alternately stacked along [001] Eu-2[BN2]I - isotypic to Sr-2[BN2]I - crystallizes in the monoclinic space group P2(1)/m (No. 11, Pearson code: mP24; Z = 4; a = 10.2548(6) angstrom, b = 4.1587(3) angstrom, c = 13.1234(9) angstrom, beta = 91.215(4)degrees). The crystal structure is characterized by slightly puckered layers formed by condensed edge-sharing I@Eu-6 octahedra which are separated by isolated [BN2](3-) units. The bond lengths for the strictly linear [BN2](3-) anions in (1) and (2) are d(B-N) = 1.351(4) angstrom and 1.356(8) angstrom, respectively. In Eu-2[BN2]I two crystallograhically distinct [BN2](3-) anions are present with d(B1-N) = 1.32(4) angstrom, 1.37(4)angstrom and d(B2-N) = 1.30(4) angstrom, 1.34(4) angstrom, respectively. Their bond angles vary slightly: angle(N-B1-N) = 179(3)degrees and angle(N-B2-N) = 177(3)degrees. The magnetic susceptibility data of the europium compounds (2) and (3) indicate that the Eu ions are divalent with 4f(7) configuration. Vibrational spectra were measured and interpreted based on the D infinity(h) symmetry of the discrete linear [N-B-N](3-) moieties, considering the site symmetry reduction and the presence of two distinct [BN2](3-) groups in (3)., NA

Single crystals of Ba2[TaN3] (monocl., C2/c (Nr. 15); a = 613.0(3), b = 1181.5(4), c = 1326.3(5) pm; β = 91.1(1)°; Ζ = 8) were prepared from mixtures of Li and Ba (molar ratio 1:1) in tantalum crucibles and by reaction with nitrogen (1 atm) at 1000°C. The crystal structure (an isotype of Ba2[ZnO3]) contains infinite tetrahedral anions ∞ 1[TaN2N2/2 4-] (Ta–N: 192.2(13)– 198.8(9) pm) which can be described as “Zweier-Einfach-Kette”. Sr2[TaN3] (monocl., C2/c (Nr. 15); a = 600.5(3), b = 1131.3(7), c = 1260.3(7) pm; β = 91.71(6)°; Ζ = 8) was obtained as a yellow powder containing excess Sr2N by reaction of Sr2N and Ta (molar ratio Sr: Ta = 4.5:1) with nitrogen (1 atm) at 1000°C. The isotypic relationship to Ba2[TaN3] was confirmed by X-ray powder investigations.

Ca2[FeN2] (monocl., C2/m (No. 12); a = 1093.0(2) pm, b = 496.0(1) pm, c = 684.4(1) pm, β = 121.09(1)°; Z = 4) and Sr2[FeN2] (tricl., P1̄ (No. 2); a = 653.8(1) pm, b = 869.0(2) pm, c = 893.2(2) pm, α = 90.22(2)°, β = 109.45(1)°, γ = 102.30(1)°; Z = 5) were prepared by reaction of mixtures Ca3N2/Fe (Sr2N/Fe) with nitrogen (1 atm) at 850 C. The crystal structure of Ca2[FeN2] contains isolated planar anions [Fe2N4]8-; in the crystal structure of Sr2[FeN2] planar [Fe2N4]8- units are present as well as linear anions [FeN2]4-.

The structural chemistry of calcium nitrides is represented by just two different intermediate phases: cubic Ca(3)N(2) (referred to as alpha-Ca(3)N(2), Mn(2)O(3) type structure) and Ca(2)N (CdCl(2) type structure). Other binary phases ("gamma-Ca(3)N(2)", "Ca(11)N(8)") have been proven to represent cyanamide nitrides, Ca(4)N(2)[CN(2)] and Ca(11)N(6)[CN(2)](2), respectively. The metastable nitride beta-Ca(3)N(2) is prepared either by reaction of freshly distilled calcium metal with nitrogen at 700 K, or by reaction of Ca(2)N with N(2) at 500 K. beta-Ca(3)N(2) transforms monotropically (T(trans) approximately 810 K) to cubic alpha-Ca(3)N(2). The crystal structure of beta-Ca(3)N(2) (rhombohedral R3c, no. 167, a=619.884(3) pm, c=1662.958(10) pm) is an isotype of the corundum structure (alpha-Al(2)O(3)) and comprises a network of NCa(6/4) octahedra that share common faces and edges. Magnetic susceptibility and electrical resistivity measurements confirm that beta-Ca(3)N(2) is a diamagnetic semiconductor.

The isotypic ternary compounds Ba3[MoN4] and Ba3[WN4] were prepared by reaction of the transition metals with barium (Ba3N2, resp.) under nitrogen. The crystal structures were determined by single crystal X-ray diffraction: Ba3[MoN4] (Ba3[WN4]): Pbca; Z = 8; a = 1083.9(3) pm (1091.8(3) pm), b = 1030.3(3) pm (1037.5(3) pm), c = 1202.9(3) pm (1209.2(4) pm). The structures contain isolated tetrahedral anions [MN4]6- (M = Mo, W) which are arranged in form of slightly distorted hexagonal layers and which are stacked along [010] with the sequence (···AB···). Two of the three Ba atoms are situated between, the third one is placed within the layers of [MN4]-groups. In this way the structures can be derived from the Na3As structure type.

Synthesis, crystal structure as well as IR- and Raman-spectroscopic properties of the new ternary azidoaurates(III) A[Au(N3)4] (A = K, Rb, Cs) are reported. The translucent orange-red compounds were prepared by reaction of the respective binary azides with HAuCl4 in aqueous solutions at room temperature. The crystal structures determined by single crystal X-ray diffraction methods are monoclinic (C2/c (No. 15), K/Rb/Cs[Au(N3)4]: a = 1049.30(9) pm / 1033.93(10) pm / 1011.9(8) pm, b = 1047.52(8) pm / 1064.20(11) pm / 1093.8(8) pm, c = 776.97(7) pm / 809.79(8) pm / 858.4(6) pm, β = 91.220(5)° / 90.322(5)° / 92.72(5)°) and provide the first examples for azidoaurates with mono-atomic cations. The unusual reduction of the lattice parameter a with increasing cation size in the isotypic series is discussed in detail. IR- and Raman-spectroscopic measurements show strongly covalent gold-nitrogen contacts, a bonding situation which is further supported by quantum chemical calculations and ELF-analyses.

The ternary alkaline-earth nitridonickelate Ba2[Ni3N2] (Ba2[NiI2Ni0N2]) was prepared by the reaction of mixtures of Ba2N and Ni in nitrogen gas of ambient back-pressure at 1173 K. The crystal structure determined by X-ray single-crystal and powder diffraction methods as well as from neutron diffraction data at various temperatures between 2 and 298 K is orthorhombic (Cmca (no. 64), 298 K: a=715.27(18) pm, b=1032.99(21) pm, c=740.12(20) pm) and provides the first example of a nitridonickelate with a two-dimensional complex anion. The Ni2 atom is described with a split position and the corresponding superstructure variants are investigated by theoretical full-potential nonorthogonal local-orbital calculations (FPLO). The average oxidation state of Ni in Ba2[Ni3N2] is +0.67, the lowest average value observed in nitridonickelates so far. Investigations of the physical properties demonstrate that Ba2[Ni3N2] acts as a "poor" metal with a large resistivity of approximately 2.7 mOmega cm at 300 K and exhibits low-dimensional magnetism with antiferromagnetic ordering at T approximately 90 K. XAS spectra correspond with low-valent Ni states.

LiSr2[CoN2] (tetrag., P42/mnm (Nr. 136); a = 524.4(1) pm, c = 730.7(2) pm; Z = 2) was prepared by reaction of mixtures of Li, Sr2N and Co (molar ratio 6:3:1) in tantalum crucibles under nitrogen (1 atm) at 850 °C. The crystal structure (α-Li3[BN2]-type) contains linear anions [Co1N2]5- (Co-N : 181.0(5) pm) which are isostructural to [Fe11N2]4- (Li4[FeN2]) as well as to the maingroup species CO2 and [BN2]3-.