Metal Nitrides Grown from Ca/Li Flux: Ca₆Te₃N₂ and New Nitridoferrate(I) Ca₆(Li_<i>x</i>Fe_1–<i>x</i>)Te₂N₃

Two new tellurium-containing nitrides were grown from reactions in molten calcium and lithium. The compound Ca₆Te₃N₂ crystallizes in space group <i>R</i>3̅<i>c</i> (<i>a</i> = 12.000(3)­Å, <i>c</i> = 13.147(4)­Å; <i>Z</i> = 6); its structure is an anti-type of rinneite (K₃NaFeCl₆) and 2H perovskite related oxides such as Sr₃Co₂O₆. The compound Ca₆(Li_<i>x</i>Fe_1–<i>x</i>)­Te₂N₃ where <i>x</i> ≈ 0.48 forms in space group <i>P</i>4₂/<i>m</i> (<i>a</i> = 8.718(3)­Å, <i>c</i> = 6.719(2)­Å; <i>Z</i> = 2) with a new stuffed anti-type variant of the Tl₃BiCl₆ structure. Band structure calculations and easily observable red/green dichroic behavior indicate that Ca₆Te₃N₂ is a highly anisotropic direct band gap semiconductor (<i>E</i>_g = 2.5 eV). Ca₆(Li_<i>x</i>Fe_1–<i>x</i>)­Te₂N₃ features isolated linear N–Fe–N units with iron in the rare Fe¹⁺ state. The magnetic behavior of the iron site was characterized by magnetic susceptibility measurements, which indicate a very high magnetic moment (5.16μ_B) likely due to a high degree of spin–orbit coupling. Inherent disorder at the Fe/Li mixed site frustrates long-range communication between magnetic centers

Synthesis and Properties of New Multinary Silicides R₅Mg₅Fe₄Al_<i>x</i>Si_{18–<i>x</i>} (R = Gd, Dy, Y, <i>x</i> ≈ 12) Grown in Mg/Al Flux

Reactions of iron, silicon, and R = Gd, Dy, or Y in 1:1 Mg/Al mixed flux produce well-formed crystals of R₅Mg₅Fe₄Al_<i>x</i>Si_{18–<i>x</i>} (<i>x</i> ≈ 12). These phases have a new structure type in tetragonal space group <i>P</i>4<i>/mmm</i> (<i>a</i> = 11.655(2) Å, <i>c</i> = 4.0668(8) Å, <i>Z</i> = 1 and <i>R</i>₁ = 0.0155 for the Dy analogue). The structure features two rare earth sites and one iron site; the latter is in monocapped trigonal prismatic coordination surrounded by silicon and aluminum atoms. Siting of Al and Si was investigated using bond length analysis and ²⁷Al and ²⁹Si MAS NMR studies. The magnetic properties are determined by the R elements, with the Gd and Dy analogues exhibiting antiferromagnetic ordering at <i>T</i>_N = 11.9 and 6.9 K respectively; both phases exhibit complex metamagnetic behavior with varying field

Reaction of Methane with Bulk Intermetallics Containing Iron Clusters Yields Carbon Nanotubes

Reaction of Methane with Bulk Intermetallics Containing Iron Clusters Yields Carbon Nanotube

Synthesis and Properties of New Multinary Silicides R₅Mg₅Fe₄Al_<i>x</i>Si_{18–<i>x</i>} (R = Gd, Dy, Y, <i>x</i> ≈ 12) Grown in Mg/Al Flux

Reactions of iron, silicon, and R = Gd, Dy, or Y in 1:1 Mg/Al mixed flux produce well-formed crystals of R₅Mg₅Fe₄Al_<i>x</i>Si_{18–<i>x</i>} (<i>x</i> ≈ 12). These phases have a new structure type in tetragonal space group <i>P</i>4<i>/mmm</i> (<i>a</i> = 11.655(2) Å, <i>c</i> = 4.0668(8) Å, <i>Z</i> = 1 and <i>R</i>₁ = 0.0155 for the Dy analogue). The structure features two rare earth sites and one iron site; the latter is in monocapped trigonal prismatic coordination surrounded by silicon and aluminum atoms. Siting of Al and Si was investigated using bond length analysis and ²⁷Al and ²⁹Si MAS NMR studies. The magnetic properties are determined by the R elements, with the Gd and Dy analogues exhibiting antiferromagnetic ordering at <i>T</i>_N = 11.9 and 6.9 K respectively; both phases exhibit complex metamagnetic behavior with varying field

Ca₁₁E₃C₈ (E = Sn, Pb): New Complex Carbide Zintl Phases Grown from Ca/Li Flux

New carbide Zintl phases Ca₁₁E₃C₈ (E = Sn, Pb) were grown from reactions of carbon and heavy tetrelides in Ca/Li flux. They form with a new structure type in space group <i>P</i>2₁/<i>c</i> (<i>a</i> = 13.1877(9)­Å, <i>b</i> = 10.6915(7)­Å, <i>c</i> = 14.2148(9)­Å, β = 105.649(1)°, and <i>R</i>₁ = 0.019 for the Ca₁₁Sn₃C₈ analog). The structure features isolated E^4– anions as well as acetylide (C₂^2–) and allenylide (C₃^4–) anions; the vibrational modes of the carbide anions are observed in the Raman spectrum. The charge-balanced nature of these phases is confirmed by DOS calculations which indicate that the tin analog has a small band gap (<i>E</i>_g < 0.1 eV) and the lead analog has a pseudogap at the Fermi level. Reactions of these compounds with water produce acetylene and allene

Ca₁₁E₃C₈ (E = Sn, Pb): New Complex Carbide Zintl Phases Grown from Ca/Li Flux

New carbide Zintl phases Ca₁₁E₃C₈ (E = Sn, Pb) were grown from reactions of carbon and heavy tetrelides in Ca/Li flux. They form with a new structure type in space group <i>P</i>2₁/<i>c</i> (<i>a</i> = 13.1877(9)­Å, <i>b</i> = 10.6915(7)­Å, <i>c</i> = 14.2148(9)­Å, β = 105.649(1)°, and <i>R</i>₁ = 0.019 for the Ca₁₁Sn₃C₈ analog). The structure features isolated E^4– anions as well as acetylide (C₂^2–) and allenylide (C₃^4–) anions; the vibrational modes of the carbide anions are observed in the Raman spectrum. The charge-balanced nature of these phases is confirmed by DOS calculations which indicate that the tin analog has a small band gap (<i>E</i>_g < 0.1 eV) and the lead analog has a pseudogap at the Fermi level. Reactions of these compounds with water produce acetylene and allene

Ca₅₄In₁₃B_4–<i>x</i>H_23+<i>x</i>: A Complex Metal Subhydride Featuring Ionic and Metallic Regions

Reactions of CaH₂ with group 13 metals in a 1:1 Ca/Li flux mixture produce Ca₅₄In₁₃B_4–<i>x</i>H_23+<i>x</i> (2.4 < <i>x</i> < 4). This compound has a complex new structure [<i>Im</i>3̅, <i>a</i> = 16.3608(6) Å, <i>Z</i> = 2] which can be viewed as a body-centered cubic array of Bergman-related clusters that are composed of a central indium atom surrounded by an icosahedron of 12 calcium atoms; hydride ions cap each face, forming a pentagonal dodecahedron that is further surrounded by a calcium shell. These In@Ca₁₂@H₂₀@Ca₃₀ clusters are surrounded by a disordered calcium indium hydride network. Indium is not completely reduced by the flux; the structure features ionic hydride regions and metallic calcium indium regions, confirmed by electronic structure calculations and ¹H and ¹¹⁵In solid-state NMR spectroscopy. This compound can therefore be viewed as a “subhydride”, akin to the alkali metal suboxides that feature ionic oxide clusters surrounded by metallic regions

Switching on a Spin Glass: Flux Growth, Structure, and Magnetism of La₁₁Mn_{13–<i>x–y</i>}Ni_<i>x</i>Al_<i>y</i>Sn_4−δ Intermetallics

Reactions of tin and manganese in a lanthanum/nickel eutectic melt in alumina crucibles produce La₁₁Mn_{13–<i>x–y</i>}Ni_<i>x</i>Al_<i>y</i>Sn_4−δ (0 ≤ <i>x</i> ≤ 3.6; 2.5 ≤ <i>y</i> ≤ 4.9; 0.6 ≤ δ ≤ 1.1) phases with the stoichiometry dependent on the reactant ratio. These compounds crystallize in a new tetragonal structure type in space group <i>P</i>4<i>/mbm</i>, with <i>a</i> = 8.4197(1) Å, <i>c</i> = 19.2414(3) Å, and <i>Z</i> = 2 for La₁₁Mn_8.2Ni_0.8Al₄Sn_3.3. The structure can be viewed as an intergrowth between La₆Co₁₁Ga₃-type layers and Cr₅B₃-type La/Sn slabs. This system represents a unique playground to study the itinerant magnetism of diluted icosahedral Mn layers. The dilution of manganese sites in the Mn/Ni/Al layer with nonmagnetic elements has a significant effect on magnetic properties, with low Mn content analogues being paramagnetic and higher Mn content analogues such as La₁₁Mn₁₀Al₃Sn_3.4 exhibiting spin-glass behavior with a freezing transition at 20 K. The lack of long-range magnetic ordering is confirmed by heat capacity and resistivity measurements

Low-Dimensional Nitridosilicates Grown from Ca/Li Flux: Void Metal Ca₈In₂SiN₄ and Semiconductor Ca₃SiN₃H

Reactions of indium and silicon with lithium nitride in Ca/Li flux produce two new nitridosilicates: Ca₈In₂SiN₄ (orthorhombic, <i>Ibam</i>; <i>a</i> = 12.904(1) Å, <i>b</i> = 9.688(1) Å, <i>c</i> = 10.899(1) Å, <i>Z</i> = 4) and Ca₃SiN₃H (monoclinic, <i>C</i>2/<i>c</i>; <i>a</i> = 5.236(1) Å, <i>b</i> = 10.461(3) Å, <i>c</i> = 16.389(4) Å, β = 91.182(4)°, <i>Z</i> = 8). Ca₈In₂SiN₄ features isolated [SiN₄]^8– units and indium dimers surrounded by calcium atoms. Ca₃SiN₃H features infinite chains of corner-sharing SiN₄ tetrahedra and distorted edge-sharing H@Ca₆ octahedra. Optical properties and band structure calculations indicate that Ca₈In₂SiN₄ is a void metal with calcium and indium states at the Fermi level and Ca₃SiN₃H is a semiconductor with a band gap of 3.1 eV

LiCa₃As₂H and Ca₁₄As₆X₇ (X = C, H, N): Two New Arsenide Hydride Phases Grown from Ca/Li Metal Flux

The reaction of arsenic with sources of light elements in a Ca/Li melt leads to the formation of two new arsenide hydride phases. The predominant phase Ca₁₄As₆X₇ (X = C^4–, N^3–, H^–) exhibits a new tetragonal structure type in the space group <i>P</i>4<i>/mbm</i> (<i>a</i> = 15.749(1) Å, <i>c</i> = 9.1062(9) Å, Z = 4, R1 = 0.0150). The minor phase LiCa₃As₂H also has a new structure type in the orthorhombic space group <i>Pnma</i> (<i>a</i> = 11.4064(7) Å, <i>b</i> = 4.2702(3) Å, <i>c</i> = 11.8762(8)­Å, Z = 4, R1 = 0.0135). Both phases feature hydride and arsenide anions separated by calcium cations. The red color of these compounds indicates they should be charge-balanced. DOS calculations on LiCa₃As₂H confirm a band gap of 1.4 eV; UV–vis spectroscopy on Ca₁₄As₆X₇ shows a band gap of 1.6 eV. Single-crystal neutron diffraction studies were necessary to determine the mixed occupancy of carbon, nitrogen, and hydrogen anions on the six light-element sites in Ca₁₄As₆X₇; these data indicated an overall stoichiometry of Ca₁₄As₆C_0.445N_1.135H_4.915