Synthesis, crystal structure and magnetic properties of an octanuclear cerium(III) complex of pyridine-2,6-dicarboxylate

An octanuclear compound of cerium(III), [Ce8(Pydc)10(HPydc)4.22H2O].11H2O (1) (Pydc=pyridine-2,6-dicarboxylate anion) was prepared under mild solvothermal conditions and its crystal structure was determined by single-crystal X-ray diffraction. Three kinds of coordination environments are observed, which include: [Ce(Pydc)3], [Ce(Pydc)(H2O)4(O,O)], and [Ce(H2O)7(O,O)]. Each cerium atom in 1 is nine-coordinated but two different geometries are found. The Ce1 and Ce2 atoms exhibit a nearly tricapped trigonal prismatic CeN3O6 geometry, while Ce3 and Ce4 possess CeNO8 and CeO9 coordination polyhedra, which approximate to slightly distorted mono-capped square antiprisms having 12 triangular faces. The Pydc ligands adopt tri-, tetra-, and penta-coordination modes through tridentate chelating and, μ2 and μ3-bridging modes, respectively. The clusters are joined by O–H···O hydrogen bonds to generate 3D supramolecular network. Magnetic susceptibility measurements for 1 indicate that the χm values obey the Curie-Weiss law. The overall magnetic behavior is typical for the presence of antiferromagnetic exchange coupling interactions between the cerium(III) ions.

Synthesis of Ce2Rh3Ge5 Crystals from a Bismuth Flux

The germanide Ce2Rh3Ge5 was synthesized from the elements in a bismuth flux, and the structure was refined from single-crystal X-ray diffractometer data: U2Co3Si5 type, Ibam, a = 1010:1(2), b = 1210:4(2), c = 599:1(1) pm, wR=0.0596, 760 structure factors, 31 variables. The rhodium and germanium atoms build up a three-dimensional [Rh3Ge5] network (242 - 269 pm Rh-Ge; 300 pm Rh-Rh; 266 pm Ge-Ge) in which the cerium atoms fill cavities. Each cerium atom has coordination number 17 by ten germanium (302 - 331 pm) and seven rhodium (320 - 355 pm) neighbors. The crystal-chemical relation of the Ce2Rh3Ge5 (≡ CeRh1:5Ge2:5) structure with that of CeRh2Ge2 (ThCr2Si2 type) is discussed.

CaAl2Si2-type Arsenides RE2/3Zn2As2 (RE = La, Ce, Pr, Nd, Sm)

The ternary arsenides RE2/3Zn2As2 (RE = La, Ce, Pr, Nd, Sm) were synthesized from the elements in NaCl/KCl salt fluxes and were characterized by powder X-ray diffraction. The Ce2/3Zn2As2 structure was refined on the basis of single-crystal X-ray diffractometer data: CaAl2Si2 type, P¯3m1, Z = 1, a = 417.17(6), c = 703.7(1) pm, wR2 = 0.0353, 211 F2 values, 11 variables, SOF(Ce) = 62.9(5) %. The zinc and arsenic atoms form a two-dimensional network of edge-sharing ZnAs4/4 tetrahedra with Zn-As distances of 253 pm. These covalently bonded [Zn2As2]2− layers are separated and charge-balanced by the cerium atoms. Each cerium atom has a slightly distorted octahedral arsenic coordination (Ce-As 302 pm). The defect type of the RE2/3Zn2As2 arsenides is discussed with respect to isotypic sulfides RE2/3Cu2S2.

Intermediate-valent Cerium in CeRu2Mg5

The magnesium-rich compound CeRu2Mg5 was synthesized by high-frequency melting of the elements in a sealed tantalum ampoule. CeRu2Mg5 crystallizes with a new tetragonal structure type: P42/ncm, a = 961.1(1), c = 723.2(1) pm, wR2 = 0.0284, 481 F2 values and 25 variables. The striking structural motifs in CeRu2Mg5 are short Ce-Ru distances of 232 pm. Each cerium atom is connected to two ruthenium atoms within a three-dimensional [Ru2Mg5] network. CeRu2Mg5 has a pronounced magnesium substructure with short Mg-Mg distances in the range 302 - 341 pm. The short Ce-Ru distances are a consequence of the almost tetravalent character of the cerium atoms. Temperature-dependent magnetic susceptibility data show intermediate-valent behavior of the cerium atoms (0.9(1) μB per formula unit) and no magnetic ordering down to 3 K.

Single Crystal Investigation and Physical Properties of the Binary Compound CeB4

The structure of CeB4 has been determined by single crystal X-ray diffraction. The compound crystallizes in the ThB4 structure type (space group P4/mbm, a = 7.2034(8), c = 4.1006(5) Å; 270 reflections with Fo ≥ 4σ (Fo), R1 = 0.023, wR2 = 0.052). The results of the magnetic and electrical resistivity measurements indicate a strong f-d hybridization of the 4 f electrons of the cerium atom