Trivalent‐Intermediate Valent Cerium Ordering in CeRuSn – A Static Intermediate Valent Cerium Compound with a Superstructure of the CeCoAl Type

New equiatomic stannide CeRuSn was synthesized from the elements by arc‐melting. CeRuSn was investigated by X‐ray powder and single crystal diffraction: C2/m, a = 1156.1(4), b = 475.9(2) and c = 1023.3(4) pm, β = 102.89(3)°, wR2 = 0.0466, 1229 F² values and 38 variables. CeRuSn adopts a superstructure of the monoclinic CeCoAl type through a doubling of the subcell c axis. In the superstructure two crystallographically independent cerium sites occur. Based on the interatomic distances the two sites can be assigned to trivalent Ce2 and intermediate valent Ce1. This trivalent‐intermediate valent cerium ordering is underlined by magnetic susceptibility measurements χ_m(T): below 150 K χ_m, measured with decreasing temperature, follows a Curie‐Weiss law χ_m = C_m/(T–θ_p) giving C_m = 0.38 emuK/mol as Curie constant per CeRuSn mol; a value showing that only half of the cerium atoms are trivalent in CeRuSn (C_m = 0.807 emuK/mol for one free Ce³⁺ ion). A remarkable feature of the CeRuSn structure are the short Ce1–Ru1 (233 pm) and Ce1–Ru2 (246 pm) distances. The crystal chemistry of CeRuSn is discussed on the basis of a group‐subgroup scheme.     

Quaternary Germanides RE3TRh4Ge4 (RE = Ce,Pr, Nd; T = Nb,Ta) – A New Coloring Variant of the Aristotype AlB2

The quaternary germanides RE₃TRh₄Ge₄ (RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc‐melting and subsequent annealing in a muffle furnace. The structure of Ce₃TaRh₄Ge₄ was refined from single‐crystal X‐ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR₂ = 0.0678, 1004 F² values, and 40 variables. Isotypy of the remaining phases was evident from X‐ray powder patterns. Ce₃TaRh₄Ge₄ is a new superstructure variant of the aristotype AlB₂ with an ordering of cerium and tantalum on the aluminum site, whereas the honey‐comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal‐chemical relationship is discussed based on a group‐subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh₄Ge₄] network, which shows the shortest interatomic distances (253–271 pm Rh–Ge) within the Ce₃TaRh₄Ge₄ structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta–Rh bonds (265–266 pm) and six longer Ta–Ge bonds (294–295 pm). The [Rh₄Ge₄] network fully separates the tantalum and cerium atoms (Ce–Ce > 387 pm, Ta–Ta > 431 pm, and Ce–Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce₃TaRh₄Ge₄. The Rh–Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge substructures.     

Einkristalle des Cer(III)‐Borosilicats Ce3[BSiO6][SiO4]

Single Crystals of the Cerium(III) Borosilicate Ce₃[BSiO₆][SiO₄] Colorless, lath‐shaped single crystals of Ce₃[BSiO₆]‐ [SiO₄] (orthorhombic, Pbca; a = 990.07(6), b = 720.36(4), c = 2329.2(2) pm, Z = 8) were obtained in attempts to synthesize fluoride borates with trivalent cerium in evacuated silica tubes by reaction of educt mixtures of elemental cerium, cerium dioxide, cerium trifluoride, and boron sesquioxide (Ce, CeO₂, CeF₃, B₂O₃; molar ratio 3 : 1 : 3 : 3) in fluxing CsCl (700 °C, 7 d) with the glass wall. The crystal structure contains eight‐ (Ce1) and ninefold coordinated Ce³⁺ cations (Ce2 and Ce3) surrounded by oxygen atoms. Charge balance is achieved by both discrete borosilicate ([BSiO₆]^5– ≡ [O₂BOSiO₃]^5–) and ortho‐silicate anions ([SiO₄]^4–). The former consists of a [BO₃] triangle linked to a [SiO₄] tetrahedron by a single vertex. The anions form layers in [001] direction alternatingly built up from [BSiO₆]^5– and [SiO₄]^4– groups while Ce³⁺ cations are located in between.     

Rare Earth Ruthenium Gallides with the Ideal Composition Ln2Ru3Ga5 (Ln = La–Nd,Sm) crystallizing with U2Mn3Si5 (Sc2Fe3Si5) Type Structure

The rare earth ruthenium gallides Ln₂Ru₃Ga₅ (Ln = La, Ce, Pr, Nd, Sm) were prepared by arc‐melting of cold‐pressed pellets of the elemental components. They crystallize with a tetragonal structure (P4/mnc, Z = 4) first reported for U₂Mn₃Si₅. The crystal structures of the cerium and samarium compounds were refined from single‐crystal X‐ray data, resulting in significant deviations from the ideal compositions: Ce₂Ru_2.31(1)Ga_5.69(1), a = 1135.10(8) pm, c = 580.58(6) pm, R_F = 0.022 for 742 structure factors; Sm₂Ru_2.73(2)Ga_5.27(2), a = 1132.95(9) pm, c = 562.71(6) pm, R_F = 0.026 for 566 structure factors and 32 variable parameters each. The deviations from the ideal compositions 2:3:5 are discussed. A mixed Ru/Ga occupancy occurs only for one atomic site. The displacement parameters are relatively large for atoms with mixed occupancy within their coordination shell and small for atoms with no neighboring sites of mixed occupancy. Chemical bonding is analyzed on the basis of interatomic distances. Ln–Ga bonding is stronger than Ln–Ru bonding. Ru–Ga bonding is strong and Ru–Ru bonding is weak. The Ga–Ga interactions are of similar strength as in elemental gallium.     

Semiconducting La2AuP3, the Metallic Conductor Ce2AuP3, and other Rare‐Earth Gold Phosphides Ln2AuP3 with Two Closely Related Crystal Structures

The compounds Ln₂AuP₃ were synthesized by reaction of the elemental components in evacuated silica tubes. Their crystal structures were determined from single‐crystal diffractometer data. The compounds with Ln = La, Ce, and Pr crystallize with an orthorhombic U₂NiC₃ type structure (Pnma, Z = 4). The structure refinement for Ce₂AuP₃ resulted in a = 774.14(6) pm, b = 421.11(4) pm, c = 1612.3(1) pm, R = 0.019 for 1410 structure factors and 38 variable parameters. For Pr₂AuP₃ a residual of R = 0.024 was obtained. Nd₂AuP₃ crystallizes with a monoclinic distortion of this structure: P2₁/c, Z = 4, a = 416.14(4) pm, b = 768.87(6) pm, c = 1647.1(2) pm, β = 104.06(1)°, R = 0.022 for 1361 F values and 56 variables. The near‐neighbor coordinations of the two structures are nearly the same. In both structures the gold and phosphorus atoms form two‐dimensionally infinite nets, where the gold atoms are tetrahedrally coordinated by phosphorus atoms with Au–P distances varying between 245.8 and 284.2 pm. Two thirds of the phosphorus atoms form pairs with single‐bond distances varying between 217.7 and 218.9 pm. Thus, using oxidation numbers the structures can be rationalized with the formulas (Ln⁺³)₂[AuP₃]^–6 and (Ln⁺³)₂Au⁺¹(P₂)^–4P^–3. Accordingly, La₂AuP₃ is a diamagnetic semiconductor. Pr₂AuP₃ is semiconducting with an antiferromagnetic ground state, showing metamagnetism with a critical field of B_c = 0.5(± 0.1) T. In contrast, the cerium compound is a metallic conductor, even though its cell volume indicates that the cerium atoms are essentially trivalent, as is also suggested by the ferro‐ or ferrimagnetic behavior of the compound.     

Structure and Magnetic Properties of Ce3Ge0.66In4.34 and Ce11Ge4.74In5.26

New indides Ce₃Ge_0.66In_4.34 and Ce₁₁Ge_4.74In_5.26 were synthesized from the elements by arc‐melting and subsequent annealing at 870 K. Single crystals were grown through special annealing procedures in sealed tantalum tubes in a high‐frequency furnace. Both compounds were investigated on the basis of X‐ray powder and single crystal data: I4/mcm, La₃GeIn₄ type, a = 848.8(1), c = 1192.0(2) pm, Z = 4, wR2 = 0.0453, 499 F² values, 17 variables for Ce₃Ge_0.66In_4.34 and I4/mmm, Sm₁₁Ge₄In₆ type (ordered version of the Ho₁₁Ge₁₀ type), a = 1199.3(2), c = 1662.0(3) pm, wR2 = 0.0507, 1217 F² values, 41 variables for Ce₁₁Ge_4.74In_5.26. The Ce₃Ge_0.66In_4.34 structure shows a mixed Ge/In occupancy on the 4c Wyckoff position. This site is octahedrally coordinated by cerium atoms. These octahedra share all edges, leading to a three‐dimensional network. The latter is penetrated by a two‐dimensional indium substructure which consists of flattened tetrahedra at In–In distances of 291 and 300 pm. The Ce₁₁Ge_4.74In_5.26 structure contains three crystallographically independent germanium sites. The latter are coordinated by eight or nine cerium neighbors. These CN8 and CN9 polyhedra are condensed to a complex network which is penetrated by a three‐dimensional indium network with In–In distances of 301–314 pm. The 16m site shows a mixed In/Ge occupancy. Chemical bonding in both compounds is dominated by the p elements. Both ternaries studied exhibit localized magnetism due to the presence of Ce³⁺ ions. The compound Ce₃GeIn₄ remains paramagnetic down to 1.72 K, whereas Ce₁₁Ge₄In₆ orders ferromagnetically at T_C = 7.5 K.     

Structure and properties of Ce3Pd3Bi4, CePdBi, and CePd2Zn3

The intermetallic cerium compounds Ce₃-Pd₃Bi₄, CePdBi, and CePd₂Zn₃ were synthesized from the elements in sealed tantalum ampoules in an induction furnace. The compounds were characterized by X-ray powder and single crystal diffraction: CeCo₃B₂ type (ordered version of CaCu₅), P6/mmm, a = 538.4(4), c = 427.7(4) pm, wR2 = 0.0540, 115 F ² values, 9 variables for CePd₂Zn₃ and Y₃Au₃Sb₄ type, I [`4]{\bar 4} 3d, a = 1005.2(2) pm, w R2 = 0.0402, 264 F ² values, 9 variables for Ce₃Pd₃Bi₄, and MgAgAs type, a = 681.8(1) pm for CePdBi. The bismuthide structures are build up from three-dimensional networks of corner-sharing PdBi₄ tetrahedra with Pd–Bi distances of 281 (Ce₃Pd₃Bi₄) and 296 pm (CePdBi), respectively. The cerium atoms are located in larger voids of coordination number 12 (Ce₃Pd₃Bi₄) and 10 (CePdBi). In CePd₂Zn₃ the cerium atoms fill larger channels within the three-dimensional [Pd₂Zn₃] network with 18 (6 Pd + 12 Zn) nearest neighbors. The three compounds contain stable trivalent cerium with experimental magnetic moments of μ_eff = 2.70(2), 2.48(1), and 2.49(1) μ_B/Ce atom for CePd₂Zn₃, Ce₃Pd₃Bi₄, and CePdBi, respectively. Susceptibility and specific heat data gave no hint for magnetic ordering down to 2.1 K.     

Syntheses and Crystal Structures of Hydrated Ternary Cerium Sulfates: Mixed‐valence K5Ce2(SO4)6·H2O and K2Ce(SO4)3·H2O

A new chemical and structural interpretation of K₅Ce₂(SO₄)₆·H₂O ( I ) and a redetermination of the structure of K₂Ce(SO₄)₃·H₂O ( II ) is presented. The mixed‐valent compound I crystallizes in the space group C2/c with a = 17.7321(3), b = 7.0599(1), c = 19.4628(4) Å, β = 112.373(1)° and Z = 4. Compound I has been discussed earlier with space group Cc. In the structure of I , there are pairs of edge sharing cerium polyhedra connected by sulfate oxygen atoms in the μ₃ bonding mode. These cerium dimers are linked through edge and corner sharing sulfate bridges, forming layers. The layers are joined by potassium ions which together with the water molecules are placed between the layers. No irregularity in the distribution of the Ce^III and Ce^IV to cause the lost of a crystallographic center of symmetry was detected. We suggest that the charge exerted by the extra f¹ electron for every cerium dimer is delocalized over the Ce1–O₂–Ce2 moiety in a non‐bonding mode. As a result, the oxidations state of each cerium ion is a mean value between III and IV at each atomic position. Compound II crystallizes in the space group C2 with a = 20.6149(2), b = 7.0742(1), c = 17.8570(1) Å, β = 122.720(1)° and Z = 8. The hydrogen atoms have been located and the absolute structure has been established. Neither hydrogen atom positions nor anisotropic displacement parameters were given in the previous reports. In compound II , the cerium polyhedra are connected by edge and corner sharing sulfate groups forming a three‐dimensional network. This network contains Z‐shaped channels hosting the charge compensating potassium ions.     

Preparation and Characterization of the Antibacterial Zn2+ or/and Ce3+ Loaded Montmorillonites

A series of modified montmorillonites including Zn²⁺ loaded montmorillonite (Zn/MMT), Ce³⁺ loaded montmorillonite (Ce/MMT) and Zn²⁺‐Ce³⁺ loaded montmorillonites (Zn‐Ce/MMT) were prepared by an ion‐exchange reaction, and characterized using X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), and scanning electron microscopy (SEM). The specific surface areas, zeta potentials and antibacterial activity of the modified montmorillonites were also investigated. Zinc and cerium were proved to be present as bivalent zinc state and trivalent cerium state in the modified montmorillonites. For the modified montmorillonites, the d₀₀₁ basal spacings increased and the particles were formed of irregular shapes. The antibacterial activity of the modified montmorillonites was enhanced with the increase of specific surface areas and zeta potentials, and Zn²⁺‐Ce³⁺ loaded montmorillonites displayed obvious synergistic antibacterial effect. When Zn/Ce atomic ratio was 1.24, the Zn‐Ce/MMT showed high antibacterial efficiency and broad‐spectrum antibacterial activity, possessing the MIC against Escherichia coli, Staphylococcus aureus, Candida albicans and Mucor of 1500, 1000, 2000 and 3000 mg·L^?1, respectively.     

Rare‐Earth‐Rich Magnesium Compounds RE23Rh7Mg4 (RE = La,Ce, Pr,Nd, Sm,Gd) with Tetrahedral Mg4 Clusters

The rare earth‐rich compounds RE₂₃Rh₇Mg₄ (RE = La, Ce, Pr, Nd, Sm, Gd) were prepared by induction‐melting the elements in sealed tantalum tubes. The new compounds were characterized by X‐ray powder diffraction. They crystallize with the hexagonal Pr₂₃Ir₇Mg₄ type structure, space group P6₃mc. The structures of La₂₃Rh₇Mg₄ (a = 1019.1(1), c = 2303.7(4) pm, wR2 = 0.0827, 1979 F² values, 69 variables), Nd₂₃Rh₇Mg₄ (a = 995.4(2), c = 2242.3(5) pm, wR2 = 0.0592, 2555 F² values, 74 variables) and Gd₂₃Rh_6.86(5)Mg₄ (a = 980.5(2), c = 2205.9(5) pm, wR2 = 0.0390, 2083 F² values, 71 variables) were refined from single crystal X‐ray diffractometer data. The three crystallographically different rhodium atoms have trigonal prismatic rare earth coordination with short RE–Rh distances (283–300 pm in Nd₂₃Rh₇Mg₄). The prisms are condensed via common edges, leading to a rigid three‐dimensional network in which isolated Mg₄ tetrahedra (312–317 pm Mg–Mg in Nd₂₃Rh₇Mg₄) are embedded. Temperature dependent magnetic susceptibility data of Ce₂₃Rh₇Mg₄ indicate Curie‐Weiss behavior with an experimental magnetic moment of 2.52(1) μ_B/Ce atom, indicative for stable trivalent cerium. Antiferromagnetic ordering is evident at 2.9 K.     

Synthesis,Crystal Structure and Magnetism of the New Oxysulfide Ce3NbO4S3

The orange cerium‐niobium‐oxysulfide Ce₃NbO₄S₃ was synthesized by the solid state reaction of CeO₂, Ce‐metal, Nb₂O₅ and sulfur at 1100 °C. The crystal structure has orthorhombic symmetry (space group Pbam, a = 7.055(1), b = 14.571(3), c = 7.627(2) Å, Z = 4) and contains isolated [Nb₂S₄O₆]¹⁰⁻ ions consisting of two strongly distorted, edge sharing NbO₃SS_2/2 octahedra. Niobium is connected to three oxygen and three sulfur atoms. The cerium atoms are eightfold coordinated by oxygen and sulfur atoms. Certain oxygen and sulfur atoms are not connected to niobium, but exclusively surrounded by cerium. By connecting these cation polyhedra, one recognizes layers of polycations perpendicular to the c‐axis. The magnetic susceptibility shows Curie‐Weiss behavior with an effective magnetic moment μ_eff = 2.63(1) μ_B/Ce in agreement with Ce³⁺. A Weiss‐constant θ_p = –12(1) K indicates weak antiferromagnetic coupling. No magnetic ordering was detected above 2 K.     

New Structure Type among Octahydrated Rare‐Earth Sulfates, β‐Ce2(SO4)3·8H2O,and a new Ce2(SO4)3·4H2O Polymorph

Syntheses, crystal structures and thermal behavior of two new hydrated cerium(III) sulfates are reported, Ce₂(SO₄)₃·4H₂O ( I ) and β‐Ce₂(SO₄)₃·8H₂O ( II ), both forming three‐dimensional networks. Compound I crystallizes in the space group P2₁/n. There are two non‐equivalent cerium atoms in the structure of I , one nine‐ and one ten‐fold coordinated to oxygen atoms. The cerium polyhedra are edge sharing, forming helically propagating chains, held together by sulfate groups. The structure is compact, all the sulfate groups are edge‐sharing with cerium polyhedra and one third of the oxygen atoms, belonging to sulfate groups, are in the S–Oμ₃–Ce₂ bonding mode. Compound II constitutes a new structure type among the octahydrated rare‐earth sulfates which belongs to the space group Pn. Each cerium atom is in contact with nine oxygen atoms, these belong to four water molecules, three corner sharing and one edge sharing sulfate groups. The crystal structure is built up by layers of [Ce(H₂O)₄(SO₄)]_nⁿ⁺ held together by doubly edge sharing sulfate groups. The dehydration of II is a three step process, forming Ce₂(SO₄)₃·5H₂O, Ce₂(SO₄)₃·4H₂O and Ce₂(SO₄)₃, respectively. During the oxidative decomposition of the anhydrous form, Ce₂(SO₄)₃, into the final product CeO₂, small amount of CeO(SO₄) as an intermediate species was detected.     

Ce2[SeO3]3 and Pr2[SeO3]3: Non‐Isostructural Oxoselenates(IV) of the Light Lanthanoids

The crystal structures of Ce₂[SeO₃]₃ and Pr₂[SeO₃]₃ have been refined from X‐ray single‐crystal diffraction data. The compounds were obtained using stoichiometric mixtures of CeO₂, SeO₂, Ce, and CeCl₃ (molar ratio 3:3:1:1) or Pr₆O₁₁, SeO₂, Pr, and PrCl₃ (molar ratio 3:27:1:2) heated in evacuated sealed silica tubes at 830 °C for one week. Ce₂[SeO₃]₃ crystallizes orthorhombically (space group: Pnma), with four formula units per unit cell of the dimensions a = 839.23(5) pm, b = 1421.12(9) pm, and c = 704.58(4) pm. Its structure contains only a single crystallographically unique Ce³⁺ cation in tenfold coordination with oxygen atoms arranged as single‐face bicapped square antiprism and two different trigonal pyramidal [SeO₃]^2? groups. The connectivity among the [CeO₁₀] polyhedra results in infinite sheets of face‐ and edge‐sharing units propagating normal to [001]. Pr₂[SeO₃]₃ is monoclinic (space group: P2₁/n) with twelve formula units per unit cell of the dimensions a = 1683.76(9) pm, b = 705.38(4) pm, c = 2167.19(12) pm, and β = 102.063(7)°. Its structure exhibits six crystallographically distinct Pr³⁺ cations in nine‐ and tenfold coordination with oxygen atoms forming distorted capped square antiprisms or prisms (CN = 9), bicapped square antiprisms and tetracapped trigonal prisms (CN = 10), respectively. The [PrO₉] and [PrO₁₀] polyhedra form double layers parallel to (111) by edge‐ or face‐sharing, which are linked by nine different [SeO₃]^2? groups to build up a three‐dimensional framework. In both compounds, the discrete [SeO₃]^2? anions (d(Se⁴⁺–O^2?) = 166–174 pm) show the typical Ψ¹‐tetrahedral shape owing to the non‐bonding “lone‐pair” electrons at the central selenium(IV) particles. Moreover, their stereochemical “lone‐pair” activity seems to flock together in large empty channels running along [010] in the orthorhombic Ce₂[SeO₃]₃ and along [101] in the monoclinic Pr₂[SeO₃]₃ structure, respectively.     

Preparation,Crystal Structure,and Magnetic Properties of Rare Earth Ruthenium and Osmium Carbides with La3.67FeC6 Type Structure

The new carbides Gd_3.67RuC₆ and Ln_3.67OsC₆ (Ln = La–Nd, Sm) were prepared by arc‐melting of cold‐pressed pellets of the elemental components. Their hexagonal (P6₃/m) La_3.67FeC₆ type crystal structure was refined from X‐ray powder diffraction data of La_3.67OsC₆ (a = 889.1(1) pm, c = 535.1(1) pm) and Pr_3.67OsC₆ (a = 874.9(2) pm, c = 523.7(1) pm). The occupancy parameters of one La and one Pr site were refined to 0.35(5) and 0.34(5), respectively, in agreement with the highest possible occupancy for steric reasons of 1/3. The C–C distances in the C₂ pairs are 139(6) pm and 137(3) pm, respectively, indicating double bonds. The environment of the osmium atoms is compatible with the 18‐electron rule. The magnetic properties of several carbides were determind with a SQUID magnetometer. The lanthanum compounds La_3.67RuC₆ and La_3.67OsC₆ are Pauli paramagnetic. The magnetic properties of the other compounds are dominated by the magnetic moments of the rare earth atoms. Most order ferrimagnetically with Curie temperatures varying between 5(± 3) and 32(± 6) K for Ce_3.67OsC₆ and Pr_3.67RuC₆, respectively. The cerium atoms in Ce_3.67RuC₆ and Ce_3.67OsC₆ are essentially trivalent, and the samarium compounds show Van Vleck behavior.     

Platinum‐Indium Polyanions in the Structures of LaPtIn4 and LnPtIn3 (Ln = La,Ce, Pr,Nd, Sm) and Structure Refinement of Ce2Pt2In

The title compounds were prepared by reacting the elements in an arc‐melting furnace and subsequent annealing. The LaRuSn₃ type structure of the new compounds LnPtIn₃ (Ln = La, Ce, Pr, Nd, Sm) was refined from single crystal X‐ray data for LaPtIn₃: Pm3n, a = 980.4(2) pm, wR2 = 0.0271, 399 F² values, 15 variables. Striking structural motifs of LaPtIn₃ are condensed distorted trigonal [PtIn₆] prisms with Pt–In distances of 269 pm. The lanthanum atoms occupy large cavities within the polyhedral network. Besides Pt–In bonding In–In bonding also plays an important role in LaPtIn₃ with In–In distances of 299 and 327 pm. The La1 position is occupied only to 91%, resulting in a composition La_0.98(1)PtIn₃. The La1 atoms show an extremely large displacement parameter indicating a rattling of these atoms in the In₁₂ cages. The so far most indium rich compound in the ternary system lanthanum‐platinum‐indium is LaPtIn₄ which was characterized on the basis of Guinier powder data: YNiAl₄‐type, Cmcm, a = 455.1(2) pm, b = 1687.5(5) pm, and c = 738.3(2) pm. The platinum atoms in LaPtIn₄ center trigonal prisms with the composition [La₂In₄]. Together with the indium atoms the platinum atoms form a complex three‐dimensional [PtIn₄] polyanion in which the lanthanum atoms occupy large hexagonal tubes. The structure of Ce₂Pt₂In is confirmed: Mo₂FeB₂‐type, P4/mbm, a = 779.8(1) pm, c = 388.5(1) pm, wR2 = 0.0466, 433 F² values, 12 parameters. It is built up from CsCl and AlB₂ related slabs with the compositions CeIn and CePt₂, respectively. Chemical bonding in the [PtIn₃] and [PtIn₄] polyanions of LaPtIn₃ and LaPtIn₄ is discussed.     

Complex Borides RERu4B4 (RE = Ce,Pr, Nd,Sm) – Bonding Peculiarities and Magnetic Properties

The rare earth borides RERu₄B₄ (RE = Ce, Pr, Nd, Sm) were synthesized from the elements by arc‐melting and their crystal structures were studied on the basis of X‐ray powder and single‐crystal diffraction: LuRu₄B₄ type, I4₁/acd, a = 747.47(8), c = 1506.4(3) pm, wR₂ = 0.0579, 362 F² values for CeRu₄B₄, a = 751.3(2), c = 1507.1(5) pm, wR₂ = 0.0724, 471 F² values for PrRu₄B₄, a = 751.0(2), c = 1506.9(6) pm, wR₂ = 0.0598, 384 F² values for NdRu₄B₄, and a = 749.1(1), c = 1506.0(3) pm, wR₂ = 0.0759, 413 F² values for SmRu₄B₄, with 18 variables per refinement. Striking structural motifs of the RERu₄B₄ structures are Ru₄ tetrahedra and B₂ dumbbells with Ru–Ru and B–B distances of 271 and 180 pm in CeRu₄B₄. The intermediate valence of cerium leads to shorter Ce–Ru distances of 292 pm. CeRu₄B₄ behaves like a Pauli paramagnet with a small room temperature susceptibility of 1.5 × 10^–4 emu · mol^–1. Chemical bonding analyses shows substantial Ru–B and B–B bonding within the [Ru₄B₄] substructure.     

Structure and properties of Ce<Subscript>3</Subscript>Pd<Subscript>3</Subscript>Bi<Subscript>4</Subscript>, CePdBi,and CePd<Subscript>2</Subscript>Zn<Subscript>3</Subscript>

The intermetallic cerium compounds Ce₃-Pd₃Bi₄, CePdBi, and CePd₂Zn₃ were synthesized from the elements in sealed tantalum ampoules in an induction furnace. The compounds were characterized by X-ray powder and single crystal diffraction: CeCo₃B₂ type (ordered version of CaCu₅), P6/mmm, a = 538.4(4), c = 427.7(4) pm, wR2 = 0.0540, 115 F ² values, 9 variables for CePd₂Zn₃ and Y₃Au₃Sb₄ type, I \({\bar 4}\)3d, a = 1005.2(2) pm, w R2 = 0.0402, 264 F ² values, 9 variables for Ce₃Pd₃Bi₄, and MgAgAs type, a = 681.8(1) pm for CePdBi. The bismuthide structures are build up from three-dimensional networks of corner-sharing PdBi₄ tetrahedra with Pd–Bi distances of 281 (Ce₃Pd₃Bi₄) and 296?pm (CePdBi), respectively. The cerium atoms are located in larger voids of coordination number 12 (Ce₃Pd₃Bi₄) and 10 (CePdBi). In CePd₂Zn₃ the cerium atoms fill larger channels within the three-dimensional [Pd₂Zn₃] network with 18 (6 Pd + 12 Zn) nearest neighbors. The three compounds contain stable trivalent cerium with experimental magnetic moments of μ_eff = 2.70(2), 2.48(1), and 2.49(1) μ_B/Ce atom for CePd₂Zn₃, Ce₃Pd₃Bi₄, and CePdBi, respectively. Susceptibility and specific heat data gave no hint for magnetic ordering down to 2.1?K.     

Ce20Mg19Zn81: a new structure type with a giant cubic cell

Icosacerium nonadecamagnesium henoctacontazinc, Ce₂₀Mg₁₉Zn₈₁, synthesized by fritting of the pure elements with subsequent arc melting, crystallizes with an unusually large cubic unit cell [space group F3m, a = 21.1979 (8) Å] and represents a new structure type among the technologically important family of ternary rare earth–transition metal–magnesium intermetallics. The majority of atoms (two Ce and five Zn) display .3m site symmetry, two Ce and one Mg atom occupy three 2.mm positions, one Mg and one Zn have 3m site symmetry, one Mg and three Zn atoms sit in ..m positions, and one Zn atom is in a general position. The Ce₂₀Mg₁₉Zn₈₁ structure can be described using the geometric concept of nested polyhedral units, by which it consists of four different polyhedral units, viz.A (Zn+Zn₄+Zn₄+Zn₁₂+Ce₆), B (Mg+Zn₁₂+Ce₄+Zn₂₄+Ce₄), C (Zn₄+Zn₁₂+Mg₆) and D (Zn₄+Zn₄+Mg₁₂+Ce₆), with the outer construction unit being an octahedron or tetrahedron. All interatomic distances in the structure indicate metallic‐type bonding.     

Oxidation‐State Analysis of Ceria by X‐ray Photoelectron Spectroscopy

Three different methods to determine the oxide‐phase concentration in mixed cerium oxide by hard X‐ray photoelectron spectroscopy are applied and quantitatively compared. Synchrotron‐based characterization of the O 1s region was used as a benchmark to introduce a method based on the weighted superposition of the Ce 3d spectra of the pure Ce³⁺ and Ce⁴⁺ phases, which was shown to lead to reliable and highly accurate determination of the mean oxidation state in mixed cerium oxides. The results obtained reveal a linear relation between the third distinct final state (u′′′) satellite peak intensity of the Ce⁴⁺ phase and the Ce⁴⁺ concentration by proper inclusion of Ce³⁺‐related plasmon satellite peaks, which contradicts previous claims of nonlinear behavior. In contrast, quantitative conventional peak‐fitting procedures were shown to be well suited for the Ce 2p region due to its relatively simple structure. Additional satellite features observed in the Ce 3d spectrum of CeO₂ were proposed to originate from plasmon contributions.     

[Be3(μ3‐O)3(MeCN)6{Be(MeCN)3}3](I)6 – ein Berylliumkomplex mit Cyclo‐(Be3O3)‐Kern und sein Hydrolyseprodukt [Be(H2O)4](I)2·2MeCN

Single crystals of [Be₃(μ₃‐O)₃(MeCN)₆{Be(MeCN)₃}₃](I)₆·4CH₃CN ( 1 ·4CH₃CN) were obtained in low yield by the reaction of beryllium powder with iodine in acetonitrile suspension, which probably result from traces of beryllium oxide containing the applied beryllium metal. The compound 1 ·4CH₃CN forms moisture sensitive, colourless crystal needles, which were characterized by IR spectroscopy and X‐ray diffraction (Space group Pnma, Z = 4, lattice dimensions at 100(2) K: a = 2317.4(1), b = 2491.4(1), c = 1190.6(1) pm, R₁ = 0.0315). The hexaiodide complex cation 1 ⁶⁺consists of a cyclo‐Be₃O₃ core with slightly distorted chair conformation, stabilized by coordination of two acetonitrile ligands at each of the beryllium atoms and by a {Be(CH₃CN)₃}²⁺ cation at each of the oxygen atoms. This unique coordination behaviour results in coplanar OBe₃ units with short Be–O distances of 155.0 pm and 153.6 pm on average of bond lengths within the cyclo‐Be₃O₃ unit and of the peripheric BeO bonds, respectively. Exposure of compound 1 ·4CH₃CN to moist air leads to small orange crystal plates of [Be(H₂O)₄]I₂·2CH₃CN ( 3 ·2CH₃CN). According to the crystal structure determination (Space group C2/c, Z = 4, lattice dimensions at 100(2) K: a = 1220.7(1), b = 735.0(1), c = 1608.5(1) pm, β = 97.97(1)°, R₁ = 0.0394), all hydrogen atoms of the dication [Be(H₂O)₄]²⁺ are involved to form O–H ··· N and O–H ··· I hydrogen bonds with the acetonitrile molecules and the iodide ions, respectively. Quantum chemical calculations (B3LYP/6‐311+G**) at the model [Be₃(μ₃‐O)₃(HCN)₆{Be(HCN)₃}₃]⁶⁺ show that chair and boat conformation are stable and that the distorted chair conformation is stabilized by packing effects.