The Metallic Zintl Phase Ba3Si4 – Synthesis,Crystal Structure,Chemical Bonding,and Physical Properties

The Zintl phase Ba₃Si₄ has been synthesized from the elements at 1273 K as a single phase. No homogeneity range has been found. The compound decomposes peritectically at 1307(5) K to BaSi₂ and melt. The butterfly‐shaped Si₄⁶⁻ Zintl anion in the crystal structure of Ba₃Si₄ (Pearson symbol tP28, space group P4₂/mnm, a = 8.5233(3) Å, c = 11.8322(6) Å) shows only slightly different Si‐Si bond lengths of d(Si–Si) = 2.4183(6) Å (1×) and 2.4254(3) Å (4×). The compound is diamagnetic with χ ≈ −50 × 10⁻⁶ cm³ mol⁻¹. DC resistivity measurements show a high electrical resistivity (ρ(300 K) ≈ 1.2 × 10⁻³ Ω m) with positive temperature gradient dρ/dT. The temperature dependence of the isotropic signal shift and the spin‐lattice relaxation times in ²⁹Si NMR spectroscopy confirms the metallic behavior. The experimental results are in accordance with the calculated electronic band structure, which indicates a metal with a low density of states at the Fermi level. The electron localization function (ELF) is used for analysis of chemical bonding. The reaction of solid Ba₃Si₄ with gaseous HCl leads to the oxidation of the Si₄⁶⁻ Zintl anion and yields nanoporous silicon.     

The Binary Silicides Eu5Si3 and Yb3Si5 – Synthesis,Crystal Structure,and Chemical Bonding

The binary silicides Eu₅Si₃ and Yb₃Si₅ were prepared from the elements in sealed tantalum tubes and their crystal structures were determined from single crystal X-ray data: I4/mcm, a = 791.88(7) pm, c = 1532.2(2) pm, Z = 4, wR2 = 0.0545, 600 F² values, 16 variables for Eu₅Si₃ (Cr₅B₃-type) and P62m, a = 650.8(2) pm, c = 409.2(1) pm, Z = 1, wR2 = 0.0427, 375 F² values, 12 variables for Yb₃Si₅ (Th₃Pd₅ type). The new silicide Eu₅Si₃ contains isolated silicon atoms and silicon pairs with a Si–Si distance of 242.4 pm. This silicide may be described as a Zintl phase with the formula [5 Eu²⁺]¹⁰⁺[Si]^4–[Si₂]^6–. The silicon atoms in Yb₃Si₅ form a two-dimensional planar network with two-connected and three-connected silicon atoms. According to the Zintl-Klemm concept the formula of homogeneous mixed-valent Yb₃Si₅ may to a first approximation be written as [3 Yb]⁸⁺[2 Si^–]^2–[3 Si^2–]^6–. Magnetic susceptibility investigations of Eu₅Si₃ show Curie-Weiss behaviour above 100 K with a magnetic moment of 7.85(5) μ_B which is close to the free ion value of 7.94 μ_B for Eu²⁺. Chemical bonding in Eu₅Si₃ and Yb₃Si₅ was investigated by semi-empirical band structure calculations using an extended Hückel hamiltonian. The strongest bonding interactions are found for the Si–Si contacts followed by Eu–Si and Yb–Si, respectively. The main bonding characteristics in Eu₅Si₃ are antibonding Si1₂-π* and bonding Eu–Si1 states at the Fermi level. The same holds true for the silicon polyanion in Yb₃Si₅.     

Ca3Ag1+xGe3–x (x = 1/3): New Transition Metal Zintl Phase with Intergrowth Structure and Alloying with Aluminum Metal

Abstract. The ternary Zintl phase Ca₃Ag_1+xGe_3–x (x = 1/3) was synthesized by the high‐temperature solid‐state technique and its crystal structure was refined from single‐crystal diffraction data. The compound Ca₃Ag_1.32Ge_2.68(1) adopts the Sc₃NiSi₃ type structure, crystal data: space group C2/m, a = 10.813(1) Å, b = 4.5346(4) Å, c = 14.3391(7) Å, β = 110.05(1)° and V = 660.48(10) ų for Z = 4. Its structure can be interpreted as an intergrowth of fragments cut from the CaGe (CrB‐type) and the CaAg_1+xGe_1–x (TiNiSi‐type) structures, and it therefore represents an alkaline‐earth member of the structure series with the general formula R_2+nT₂X_2+n with n = 4. Unlike the rare‐earth homologues that are fully ordered phases, one seventh of the atomic sites in the unit cell of the title compound are mixed occupied (roughly 2/3Ge and 1/3Ag), and this can be explained by the Zintl concept. The alloying of this phase using aluminum metal yielded the isotypic solid solution Ca₃(Ag/Al)_1+xGe_3–x, in which the aluminum for silver substitution is strictly localized in the TiNiSi substructure, revealing the very different functionality of the two building blocks.     

Preparation and Crystal Structure of the Clathrate‐I Cs8–xGe44+y□2–y

The clathrate‐I phase Cs_8–xGe_44+y□_2–y (space group Pm$\bar{3}$ n) was prepared by high‐pressure high‐temperature reactions of Cs₄Ge₄ and α‐Ge. Different reaction conditions were found to have a strong influence on the lattice parameter of the clathrate‐I phase ranging from 10.8070(2) Å to 10.8493(3) Å. A single crystal with composition Cs₈Ge_44.40(2)□_1.60(2) was obtained from a sample with a = 10.8238(2) Å (niobium ampoule, p = 3.4 GPa, T_max = 1400 °C). Structure analysis based on X‐ray single crystal data shows unambiguously an excess of germanium atoms with respect to the electron balanced composition Cs₈Ge₄₄□₂ on basis of the Zintl concept.     

Synthesis,Crystal Structure,and Magnetic Property of New Trispin Ln(III)‐Nitronyl Nitroxide Complexes

Four Ln(III) complexes based on a new nitronyl nitroxide radical have been synthesized and structurally characterized: {Ln(hfac)₃[NITPh(MeO)₂]₂} (Ln = Eu( 1 ), Gd( 2 ), Tb( 3 ), Dy( 4 ); NITPh(MeO)₂ = 2‐(3′,4′‐dimethoxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide; hfac = hexafluoroacetylacetonate). The single‐crystal X‐ray diffraction analysis shows that these complexes have similar mononuclear trispin structures, in which central Ln(III) ion is eight‐coordinated by two O‐atoms from two nitroxide groups and six O‐atoms from three hfac anions. The variable temperature magnetic susceptibility study reveals that there exist ferromagnetic interactions between Gd(III) and the radicals, and antiferromagnetic interactions between two radicals (J_Gd‐Rad = 3.40 cm^?1, J_Rad‐Rad = ?9.99 cm^?1) in complex 2 . Meanwhile, antiferromagnetic interactions are estimated between Eu(III) (or Dy(III)) and radicals in complexes 1 and 4 , and ferromagnetic interaction between Tb(III) and radicals in complex 3 , respectively.     

Crystal Structure and Magnetic Characteristics of a New 3‐Methylisoquinolinium Tetrachloridoferrate(III)

The crystal structure of a new 3‐methylisoquinolinium[3‐Me(IsoQH)] salt, [3‐Me(IsoQH)][FeCl₄], was determined. The iron cation is tetracoordinated by chlorine anions, and it adopts a slightly distorted tetrahedral coordination. In the crystal structure, there are π ··· π stacking interactions between the 3‐methylisoquinolinium cations in an ABAB infinite arrangement, N–H ··· Cl hydrogen bonds, and C–H ··· Cl intermolecular interactions. Magnetic measurements of a powdered sample were carried out. A negative Weiss constant as well as the intermolecular exchange parameter for [3‐Me(IsoQH)][FeCl₄] indicate the occurrence of antiferromagnetic interactions transmitted in the crystal lattice.     

Dimensions of the Ozonide Anion in M([18]crown‐6)O3·x NH3 with M = K (x = 2), Rb (x = 1) and Cs (x = 8)

Reaction of alkali metal ozonides (KO₃, RbO₃ and CsO₃) with [18]crown‐6 in liquid ammonia yields compounds of the composition M([18]crown‐6)O₃·x NH₃ with M = K (x = 2), Rb (x = 1) and Cs (x = 8). The large intermolecular distance between adjacent radical anions in these compounds leads to almost ideal paramagnetic behavior according to Curie's law. Discrepancies concerning the structure of the ozonide anions in the K and Cs compound compared to a former investigation on Rb([18]crown‐6)O₃·NH₃ have been resolved by means of DFT calculations and a single‐crystal structure redetermination.     

Eu4Bi3: Crystal Structure,Magnetic and Electronic Properties

The Eu? Bi system contains the phases Eu₅Bi₃, Eu₄Bi₃ and Eu₁₁Bi₁₀. The structure types of these phases have been determined by powder X-ray diffraction. Crystals of Eu₄Bi₃ (cubic, space group I4 3d; a = 9.920 Å, Z = 4, T = 130 K, R1/wR2 = 4.86/10.84%) were obtained in low yield by reaction of Eu, Mn, and Bi in the ratio 14:1:11 in a closed niobium tube (heating rate 30°C/h; reaction at 1050°C for 300 h, cooling rate 100°C/h). The crystal structure consists of distorted octahedra made up of six Bi coordinated to a central Eu atom. Eu is also coordinated to a three other Eu atoms and forms a three-dimensional network composed of interconnected rings. The Bi atoms are coordinated to eight Eu atoms. High yields of Eu₄Bi₃ can be prepared by reacting stoichiometric amount of the elements in a sealed tantalum tube at 1100°C for 24 h. Temperature dependent magnetic susceptibility is consistent with antiferromagnetic behavior with an ordering temperature of 18 K. The data could be fit with the Curie-Weiss law and a moment of 7.38 μ_B/Eu is obtained, consistent with all Eu atoms being Eu¹¹. Temperature dependent resistivity indicates that Eu₄Bi₃ is a metal with a room temperature resistance of 1.3 Ωcm.     

Zintl‐Phase Sr3LiAs2H: Crystal Structure and Chemical Bonding Analysis by the Electron Localizability Approach

The compound Sr₃LiAs₂H was synthesized by reaction of elemental strontium, lithium, and arsenic, as well as LiH as hydrogen source. The crystal structure was determined by single‐crystal X‐ray diffraction: space group Pnma; Pearson symbol oP28; a = 12.0340(7), b = 4.4698(2), c = 12.5907(5) Å; V = 677.2(1) ų; R_F = 0.047 for 1021 reflections and with 36 parameters refined. The positions of the hydrogen atoms were first revealed by the electron localizability indicator and subsequently confirmed by crystal structure refinement. In the crystal structure of Sr₃LiAs₂H the metal atoms are arranged in a Gd₃NiSi₂‐type motif, whereas the hydrogen atoms are arranged in a distorted tetrahedral environment formed by strontium. The calculated band structure revealed that Sr₃LiAs₂H is a semiconductor, which is in agreement with its diamagnetic behavior. Thus, Sr₃LiAs₂H is considered as a (charge‐balanced) Zintl phase.     

Darstellung,Kristallstrukturen und Schwingungsspektren von Verbindungen mit den linearen Dipnictidoborat(3–)‐Anionen [P–B–P]3–, [As–B–As]3– und [P–B–As]3–

Synthesis, Crystal Structure, and Vibrational Spectra of Compounds with the Linear Dipnictidoborate (3–) Anions [P–B–P]^3–, [As–B–As]^3–, and [P–B–As]^3– The alkali metal boron compounds M₃[BX₂] with X = P, As are synthesized from the alkali metals M and the binary components MX or M₄X₆ and BX in sealed steel ampoules (phosphides) or niobium ampoules (arsenides) at 1000 K. The compounds are obtained as bright yellow prisms (M₃[BP₂]) or plates (K₂Na[BP₂]) and yellow‐red prismatic crystals (M₃[BAs₂], Cs₃[BPAs]) which are very sensitive against oxidation and hydrolysis. Three different structure types are formed, namely K₂Na[BP₂] (C2/m (No. 12); Z = 4; a new mC24 structure type); Na₃[BP₂] (P2₁/c (No. 14); Z = 4, β‐Li₃[BN₂] type), M₃[BX₂] with M = K, Rb, Cs and X = P, As and Cs₃[P–B–As] (C2/c, (No. 15); Z = 4, K₃[BP₂] type). The bond lengths of the linear [BX₂]^3– anions are hardly changed and correspond to a Pauling bond order PBO = 1.9 (d(B–P) = 176.7–177.1 pm; d(B–As) = 186.5–188.0 pm). The vibrational spectra confirm the existence of unmixed and mixed units [P–B–P]^3–, [As–B–As]^3– and [P–B–As]^3– with D_∞h and C_∞v symmetry, respectively. The valence force constants f(B–X) and the corresponding Siebert bond orders, calculated from the frequencies, are discussed and compared with those of the isoelectronic anions and molecules.     

Die Reaktionen von M[BF4] (M = Li,K) und (C2H5)2O·BF3 mit (CH3)3SiCN. Bildung von M[BFx>(CN)4—x] (M = Li,K; x = 1, 2) und (CH3)3SiNCBFx(CN)3—x, (x = 0, 1)

The Reactions of M[BF₄] (M = Li, K) and (C₂H₅)₂O·BF₃ with (CH₃)₃SiCN. Formation of M[BF_x(CN)_4—x] (M = Li, K; x = 1, 2) and (CH₃)₃SiNCBF_x(CN)_3—x, (x = 0, 1) The reaction of M[BF₄] (M = Li, K) with (CH₃)₃SiCN leads selectively, depending on the reaction time and temperature, to the mixed cyanofluoroborates M[BF_x(CN)_4—x] (x = 1, 2; M = Li, K). By using (C₂H₅)₂O·BF₃ the synthesis yields the compounds (CH₃)₃SiNCBF_x(CN)_3—x x = 0, 1. The products are characterized by vibrational and NMR‐spectroscopy, as well as by X‐ray diffraction of single‐crystals: Li[BF₂(CN)₂]·2Me₃SiCN Cmc2₁, a = 24.0851(5), b = 12.8829(3), c = 18.9139(5) Å V = 5868.7(2) ų, Z = 12, R₁ = 4.7%; K[BF₂(CN)₂] P4₁2₁2, a = 13.1596(3), c = 38.4183(8) Å, V = 6653.1(3) ų, Z = 48, R₁ = 2.5%; K[BF(CN)₃] P1¯, a = 6.519(1), b = 7.319(1), c = 7.633(2) Å, α = 68.02(3), β = 74.70(3), γ = 89.09(3)°, V = 324.3(1) ų, Z = 2, R₁ = 3.6%; Me₃SiNCBF(CN)₂ Pbca, a = 9.1838(6), b = 13.3094(8), c = 16.840(1) Å, V = 2058.4(2) ų, Z = 8, R₁ = 4.4%     

Magnetic Ordering in the Solid Solution CePt1–xPdxAl (x = 0.1–0.8)

In order to investigate the magnetic properties of the solid solution CePt_1–xPd_xAl the individual compounds were synthesized from the elements using an arc furnace. From x = 0–0.8 the solid solution crystallizes in the orthorhombic TiNiSi‐type structure (Pnma, no. 62; a = 721–722, b = 448–453 and c = 778–779 pm) and for x = 0.9 both the TiNiSi‐ as well as the hexagonal ZrNiAl‐type structures were observed. The solid solution exhibits an interesting magnetic behavior as for small values of x ferromagnetic ordering can be found. At higher palladium content this changes towards an antiferromagnetic ordering. Furthermore the solid solution exhibits a spin‐reorientation (meta‐magnetic step) for x = 0.2–0.7.     

Synthesis and structural characterization of the type‐I clathrates K8AlxSn46–x and Rb8AlxSn46–x (x ≃ 6.4–9.7)

Exploratory studies in the systems A–Al–Sn (A = K and Rb) yielded the clathrates K₈Al_xSn_46–x (potassium aluminium stannide) and Rb₈Al_xSn_46–x (rubidium aluminium stannide), both with the cubic type‐I structure (space group Pmn, No. 223; a ? 12.0 Å). The Al:Sn ratio is close to the idealized A₈Al₈Sn₃₈ composition and it is shown that it can be varied slightly, in the range of ca ±1.5, depending on the experimental conditions. Both the (Sn,Al)₂₀ and the (Sn,Al)₂₄ cages in the structure are fully occupied by the guest alkali metal atoms, i.e. K or Rb. The A₈Al₈Sn₃₈ formula has a valence electron count that obeys the valence rules and represents an intrinsic semiconductor, while the experimentally determined compositions A₈Al_8±xSn_38?x suggest the synthesized materials to be nearly charge‐balanced Zintl phases, i.e. they are likely to behave as heavily doped p‐ or n‐type semiconductors.     

Phosphorus Oligomerization in Zintl Phases: Synthesis,Crystal Structure,and Bonding Analysis of Mixed Alkali and Alkaline‐Earth Metal Phosphides

Pnictides α‐Ba₅P₄ and KBa₄P₅ were prepared by melting the elements. The α‐Ba₅P₄ compound crystallizes in the orthorhombic system (Sm₅Ge₄‐type), space group Pnma, Z = 4, a = 8.330(3), b = 16.503(3), c = 8.405(2)Å, it contains two anionic species : P₂^4— dumbbells and P^3—. The KBa₄P₅ compound crystallizes in the tetragonal system, space group P4₃2₁2, Z = 4, a = 8.559(1), c = 16.102(2)Å, it contains trimers P₃^5— and dumbbells P₂^4—. The crystal structures were solved from single crystal X‐ray data and refined by full‐matrix least‐squares to agreement factors R1 = 0.047 and 0.038, respectively. Using ionic charges, α‐Ba₅P₄ is formulated as [5Ba²⁺, 2P^3—, P₂^4—] and KBa₄P₅ as [K⁺, 4Ba²⁺, P₂^4—, P₃^5—]. The level of oligomerisation in these structures depends upon the overall valence electron content, bonding within the anionic oligomers has been analyzed on the basis of EHMO calculations and compared to classical or hypervalent bonding in other phosphide compounds.     

Reactions in Anhydrous Liquid Ammonia: Syntheses and Crystal Structures of [M(NH3)8]I2 (M = Eu,Yb) with Bicapped Trigonal-Prismatic Octaammine Lanthanoid(II) Cations

The compounds [M(NH₃)₈]I₂ (M = Eu, Yb) were obtained from reactions in anhydrous liquid ammonia solutions as side products. They were characterized by single-crystal X-ray diffraction and found to be isotypic to the compounds [Ca(NH₃)₈]X₂ (X = Cl, Br, I). The coordination sphere of the lanthanoid(II) cations is not square-antiprismatic but much better described as bicapped trigonal-prismatic. In contrast, quantum-chemical gas-phase calculations show the square-antiprismatic coordination polyhedron (point group S₈) to be energetically favored over the bicapped trigonal prism and the latter is not even a true local minimum. Obviously, hydrogen bonding and eventually other weak interactions have an impact on the observed bicapped trigonal-prismatic coordination sphere of the [M(NH₃)₈]²⁺ cations in the solid state.     

Synthesis,Crystal Structure,Thermal Stability,Magnetic Property,and Biological Activity of a New Copper(II) Complex Based on 1,2,4‐Benzenetricarboxylic Acid and 2,2′‐Bipyridine

Based on an asymmetric 1,2,4‐benzenetricarboxylic acid (H₃btc) and 2,2′‐bipyridine (bpy), a new Cu^II complex, Cu₂(H₂btc)₄(bpy)₂ · 8H₂O ( 1 ), was synthesized and structurally characterized by single‐crystal X‐ray diffraction, hirshfeld surface (HS) analysis, IR spectroscopy, powder X‐ray analysis, thermal gravimetry analysis (TGA), magnetic susceptibility, EPR measurement, and UV/Vis spectrometry. Complex 1 shows a dinuclear copper structure. The Cu^II of each dinuclear moiety are in a slightly distorted square‐pyramidal environments. Magnetic susceptibility of 1 shows a ferromagnetic coupling between both metal atoms. The interaction of 1 with bovine serum albumin (BSA) is investigated using UV/Vis, fluorescence spectroscopic methods. The Cu^II complex shows strong binding propensity in albumin binding study.     

Gradual Cerium Valence Change in the Solid Solution CeRu1–xPdxAl (x = 0.1–0.9)

The solid solution CeRu_1–xPd_xAl was synthesized for x = 0.1–0.9 from the elements by arc‐melting and subsequent annealing and characterized by powder X‐ray diffraction. All members crystallize in the orthorhombic LaNiAl type structure, space group Pnma. The lattice parameters range from a = 718–722, b = 412–426, and c = 1588–1620 pm, but no linear change of the lattice parameters was found. Magnetic measurements reveal intermediate cerium valences, which change to more trivalent cerium with increasing Pd content. The susceptibility data was interpreted by either the Inter‐Configuration Fluctuation (ICF) model or the Curie‐Weiss law.