Contributions to the Chemistry of the Binary Compounds of the Transition Elements

Phase and structural relationships of the sulfur, selenium, and tellurium compounds of the 4d and 5d transition elements of groups IV to VII of the periodic system are discussed. Homologous elements behave very similarly with respect to the chalcogens, and this is particularly the case for niobium and tantalum, and for molybdenum and tungsten. However, zirconium, niobium, and molybdenum have a greater tendency towards formation of chalcogen-poor phases than their homologues hafnium, tantalum, and tungsten. Subchalcogenides are known only for zirconium and niobium. The number of phases and the tendency towards formation of solid solutions are considerably smaller among the tellurides than among the sulfides and selenides. The crystal structures of the telluride phases also differ from those of the sulfide and selenide phases of analogous composition. In addition, a review of the phase and structural relationships of the arsenic and antimony compounds of the 4d and 5d transition elements of groups V to VII is given.     

Unusual Solid Solutions in the System Ge‐Sb‐Te: The Crystal Structure of 33R‐Ge4−xSb2−yTe7 (x,y ≈ 0.1) is Isostructural to that of Ge3Sb2Te6

Whereas for a series of layered compounds with the general formula (GeTe)_n(Sb₂Te₃)_m the stoichiometry allows to predict the structure type and the average thickness of the hexagonal atom layers, these rules are not generally applicable for GeTe‐rich compounds like Ge₄Sb₂Te₇. A 39R layer stacking is expected, however, single crystal diffraction studies reveal a 33R layered structure ( , a = 4.1891(5) Å, c = 62.169(15), R = 0.047) closely related to that of Ge₃Sb₂Te₆. This is also corroborated by the average layer thickness that can be determined from the strong reflections of powder patterns and exhibits a direct relation to the structure type. Mixed occupancy of cation positions with Ge and Sb and possibly defects allow this unusual range of homogeneity. Bulk material of the kinetically stable compound can be synthesized by quenching stoichiometric melts of the pure elements and subsequent annealing.     

Specific heat studies on pristine and oxygenated iron tellurides

Specific heat studies carried out on Fe_1.1Te and oxygenated Fe_1.1Te and FeTe₂ in the range 77-300 K exhibit interesting behavior. The specific heat of the pristine sample reveals a well known structural transition associated with antiferromagnetic ordering near 67 K with a small thermal hysteresis of ∼1 K. Contrastingly, the oxygenated samples exhibit a phase transition with a very large thermal hysteresis of ∼100 K. The specific heat transition observed at the 150 and 260 K regions in the oxygenated Fe_1.1Te sample could not be captured by the magnetization measurements indicating that specific heat transitions seen in oxygenated samples may not be of magnetic origin.     

Preparation and Characterization of Methyl Substituted 2,2′-Dipyridyl Diselenides and -Ditellurides: X-ray Structure of 6,6′-Dimethyl-2,2′-dipyridyl Diselenide

A convenient method for the preparation of various methyl substituted 2,2'-dipyridyl diselenides and -ditellurides by the aerial oxidation of lithium 2-pyridylselenolate/tellurolate, prepared from the lithium-halogen exchange between n-butyllithium and 2-bromo methyl substituted pyridines is reported. All the compounds prepared are new and have been characterized by elemental analysis, IR, 1 H, 13 C, 11 Se NMR, and mass spectral studies. Crystal structure of 6,6'-dimethyl-2,2'-dipyridyl diselenide has been determined.     

Rapid Oxidation of Selenides,Selenoxides, Tellurides,and Telluroxides with Aqueous Sodium Hypochlorite

A simple and convenient procedure for the rapid oxidation of a variety of selenides, selenoxides, tellurides, and telluroxides with aqueous sodium hypochlorite to selenones and tellurones, respectively, has been reported in dimethylformamide at ambient temperature.     

The coupling of butylvinyltellurides with organometallic reagents catalysed by nickel complexes

Vinylic tellurides couple efficiently with sp, sp² and sp³ hybridised organometallic compounds (Li, MgX and Zn species) in the presence of dichloro-bis(triphenylphosphine)nickel(II) as catalyst.     

Er17Ru6Te3: A highly condensed metal-rich ternary telluride

Er₁₇Ru₆Te₃ is obtained from high-temperature solid-state reactions in tantalum ampoules. The structure according to single-crystal X-ray diffraction is monoclinic, C2/m (no. 12), Z=4, a=40.185(8) Å, b=3.9969(8) Å, c=16.037(3) Å, β=95.12(3)°, V=2565.5(9) Å³. The condensed structure consists of a complex intermetallic network of intergrown sheets of edge-sharing tetrakaidecahedra (tricapped trigonal prisms, TCTP), and pairs of rectangular-face-sharing bicapped trigonal prisms (BCTP) built of erbium and centered by ruthenium. This array also contains isolated columns of TCTP erbium normal to these sheets that contain tellurium. Basal face sharing of all Er polyhedra along the short b-axis gives rise to the three-dimensional network. Synthesis and the crystal structure of the compound are discussed.     

Synthese und Kristallstruktur von Ln2SeSiO4 (Ln = Sm,Dy, Ho) und Sm2TeSiO4

Synthesis and Crystal Structure of Ln₂SeSiO₄ (Ln = Sm, Dy, Ho) and Sm₂TeSiO₄ Single crystals of Ln₂SeSiO₄ (Ln = Sm, Dy, Ho) could be prepared by the reaction of lanthanide metal, selenium and iodine in the ratio 1 : 1 : 2.5 and subsequent reaction with quartz glass powder. Black crystals of Sm₂TeSiO₄ have been obtained in chemical transport experiments of SmTe₂ with iodine in evacuated quartz glass ampoules as by‐products. All chalcogenide silicates crystallize orthorhombically with the space group Pbcm (Z = 4) and the lattice constants: Sm₂SeSiO₄: a = 612.6(1) pm, b = 709.0(1) pm, c = 1094.0(2) pm; Dy₂SeSiO₄: a = 603.6(1) pm, b = 696.4(1) pm, c = 1081.2(2) pm; Ho₂SeSiO₄: a = 601.0(1) pm, b = 693.6(1) pm, c = 1078.6(2) pm; Sm₂TeSiO₄: a = 623.82(8) pm, b = 713.06(7) pm, c = 1112.26(11) pm. The crystal structure is built up of alternating Ln(Se/Te) and LnSiO₄ sheets parallel (001).