B4 Tetrahedra for Aluminum Atoms—A Surprising Substitution in τ-Borides Ni20Al3B6 and Ni20AlB14

Stabilized by the tailor-made coordination in the crystal , B₄ tetrahedra were characterized for the first time in a solid-state structure (shown on the right). Some of the Al atoms are replaced by B₄ tetrahedra in the cubic τ-boride Ni₂₀AlB₁₄. The B–B distances of 1.681(15) Å are similar to those in the molecular structures of B₄Cl₄ and B₄(tBu)₄, which contain tetrahedral B₄ units.     

Mg3Ni20P6 und Mn3Ni20P6 — Zwei neue Phosphide mit Cr23C6-Struktur

Mg₃Ni₂₀P₆ and Mn₃Ni₂₀P₆ - Two new Phosphides with Cr₂₃C₆-type Structure The crystal structures of Mg₃Ni₂₀P₆ (a = 11.113(3)A) and Mg₃Ni₂₀P₆ (a = 11.085(1)Å) were determined by single crystal X-ray investigations. Both compounds, prepared by heating appropriate mixtures of the elements, crystallize in a ternary variant of the Cr₂₃C₆-type structure (Fm3m), which is well-known due to a large number of ternary borides.     

ChemInform Abstract: The Crystal Structures of Ni3+xSn4Zn and Ni6+xSn8Zn and Their Structural Relations to Ni3+xSn4, NiSn and Ni5‐δZnSn4.

Two new compounds, Ni_3+xSn₄Zn (x≈1.35, monoclinic, space group I2/m, Z = 2, single crystal XRD) and Ni_6+xSn₈Zn (x≈1.35, monoclinic, space group C2/m, Z = 2) are prepared by solid state reaction of the elements (Al₂O₃ crucible in evacuated quartz tubes, 1453 K).     

The Crystal Structure of ζ2‐Al3Cu4‐δ

The crystal structure of the ζ₂‐phase Al₃Cu_4‐δ was determined by means of X‐ray powder diffraction: a = 409.72(1) pm, b = 703.13(2) pm, c = 997.93(3) pm, space group Imm2, Pearson symbol oI24‐3.5, R_I = 0.0696. ζ₂‐Al₃Cu_4‐δ forms a distinctive a × √3a × 2c superstructure of a metal deficient Ni₂In‐type‐related structure. The phase is meta‐stable at ambient temperature. Between 400 °C and 450 °C it decomposes into ζ₁‐Al₃Cu₄ and η₂‐AlCu. Entropic contributions to the stability of ζ₂‐Al₃Cu_4‐δ are reflected in three statistically or partially occupied sites.     

Die Zinn-Rhodiumboride SnRh3B1−x,Sn4Rh6B und Sn5Rh6B2

The Tin Rhodium Borides SnRh₃B_1–x, Sn₄Rh₆B, and Sn₅Rh₆B₂ The new compounds SnRh₃B_1–x (x ～ 0.2, tetragonal, P4/mbm, a = 570.31(2) pm, c = 835.99(8) pm, Z = 4, 514 reflexions, 26 parameters, R = 0.026), Sn₄Rh₆B (hexagonal, P6₃/mmc, a = 560.01(3) pm, c = 1367.5(1) pm, Z = 2, 746 reflexions, 17 parameters, R = 0.035), and Sn₅Rh₆B₂ (hexagonal, P6 2m, a = 654.80(7) pm, c = 557.32(9) pm, Z = 1, 361 reflexions, 16 parameters, R = 0.039) were prepared by reaction of the elements. SnRh₃B_1–x crystallizes with the filled U₃Si type of structure, a distortion variant of the cubic perovskite; the structure of Sn₄Rh₆B may be derived from the hexagonal perovskite BaNiO₃. Both compounds contain nearly regular Rh₆B-octahedra. Sn₅Rh₆B₂ with the Sn₅Ir₆B₂ type of structure contains isolated colums composed of trigonal Rh₆B-prisms.     

Ni5‐δSn4Zn (δ ∼ 0.25) from single‐crystal data

Work on the ternary Ni–Sn–Zn phase diagram revealed the existence of the title compound pentanickel tetratin zinc, Ni_3.17Sn_2.67Zn_0.67 [Schmetterer et al. (2012). Intermetallics, doi:10.1016/j.intermet.2011.05.025]. It crystallizes in the Ni₅Ga₃Ge₂ structure type (orthorhombic, Cmcm) and is related to the InNi₂ type (hexagonal, P6₃/mmc) of the neighbouring Ni₃Sn₂ high‐temperature (HT) phase, but is not a superstructure. The crystal structure was determined using single‐crystal X‐ray diffraction. Its homogeneity range was characterized using electron microprobe analysis. Phase analysis at various temperatures indicated that the phase decomposes between 1073 and 1173 K, where a more extended ternary solid solution of the Ni₃Sn₂ HT phase was found instead.     

Synthesis and Crystal Structure of [Nd(η6‐1, 3, 5‐C6H3Me3)‐(AlCl4)3](C6H6) and Structural Comparison of Ln(η6‐arene)‐(AlCl4)3

Reaction of Ndcl₃ with AlCl₃ and mesitylene in benzene gives complex [Nd(η⁶‐1, 3, 5‐C₆H₃Me₃)‐(AlCl₄)₃](C₆H₆) (1) which was characterized by elemental analysis, IR spectra, MS and X‐ray diffractions. The X‐ray determination indicates that 1 has a distorted pentagonal bipyramidal geometry and crystallizes in the monoclinic, space group P2₁/n with a = 0.9586(2), b = 1.1717(5), c = 2.8966(7) nm, β = 90.85 (2)°, V = 3.2529 (6) nm³,D_c= 1.573 g/cm³, Z = 4. A comparison of bond parameters for all the reported Ln (η⁶‐Ar) (AlCl₄)₃ complexes indicates that the bond distance of La? C is shortened with the increasing of methyl group on benzene and with the decreasing of radius of lanthanide ions.     

5β,6β‐Epoxy‐17‐oxoandrostan‐3β‐yl acetate and 5β,6β‐epoxy‐20‐oxopregnan‐3β‐yl acetate

In the title compounds, C₂₁H₃₀O₄, (I), and C₂₃H₃₄O₄, (II), respectively, which are valuable intermediates in the synthesis of important steroid derivatives, rings A and B are cis‐(5β,10β)‐fused. The two molecules have similar conformations of rings A, B and C. The presence of the 5β,6β‐epoxide group induces a significant twist of the steroid nucleus and a strong flattening of the B ring. The different C17 substituents result in different conformations for ring D. Cohesion of the molecular packing is achieved in both compounds only by weak intermolecular interactions. The geometries of the molecules in the crystalline environment are compared with those of the free molecules as given by ab initio Roothan Hartree–Fock calculations. We show in this work that quantum mechanical ab initio methods reproduce well the details of the conformation of these molecules, including a large twist of the steroid nucleus. The calculated twist values are comparable, but are larger than the observed values, indicating a possible small effect of the crystal packing on the twist angles.