Electronic structure of the high symmetrical compounds of f-element. Part 33. A novel experimental crystallized trigonal-bipyramidal coordinated lanthanide(III) systems: Pr[N(SiMe3)2](CNR)2 (R = tBu, C6H11)]

The absorption und magnetic circular dichroism spectra of the dissolved trigonal-bipyramidal complex Pr[N(SiMe3)2]3(CNtBu)2 (1) as well as the luminescence and absorption spectra of both solid 1 and solid Pr[N(SiMe3)2]3(CNC6H11)2 (2) (pellets, unoriented single crystals) were measured at ambient and low temperatures. Because of the violation of the selection rules for D3h symmetry by both compounds a reliable crystal field(CF) splitting pattern for the ground manifold 3H4, but only a plausible for the f 2 configuration could be derived on the basis of these measurements. The latter could be simulated with a reduced r.m.s. deviation of 32.6 cm(-1) for 29 assignments by fitting the free parameters of a phenomenological Hamiltonian. The adequacy of the calculated wavefunctions of this fit in the low energy range is proved by the excellent agreement of calculated and experimental temperature dependence of mu2(eff) for compound 1. The CF parameters of this fit are considered as a "master set" of CF parameters for future CF analyses of the electronic structures of trigonal bipyramidally coordinated lanthanide(III) systems.     

Superconductivity in the Nb cluster compounds Nb3(X,Y)4 with X, Y  S,Se, Te

The Nb-chalcogenides Nb₃X₄ [1–3] with X = S, Se and Te, and Nb₃S_1.7Se_2.3 were prepared from the elements using transport reactions with iodine at temperatures between about 730 and 1050°C. The ternary compound Nb₃S_1.7Se_2.3 was confirmed to be isostructural with the hexagonal Nb₃X₄ of the space group $\text{P6}{}_3\text{m}$. The Nb₃X₄-compounds were found to be superconductors, the transition temperatures to superconductivity reaching from 1.8 to 4.0 K.     

Spektroskopische und strukturelle Charakterisierung von Tris(2, 6‐di‐t‐butyl‐phenolato)lanthanid(III) (Ln(OAr′)3; Ln = Pr,Nd) sowie parametrische Analyse des Kristallfeld‐Aufspaltungsmusters von Nd(OAr′)3

Electronic Structures of Highly Symmetrical Compounds of f Elements. 37 [1] Spectroscopic and Structural Characterization of Tris(2, 6‐di‐t‐butyl‐phenolato)lanthanide(III) (Ln(OAr′)₃; Ln = Pr, Nd), and Parametric Analysis of the Crystal Field Splitting Pattern of Nd(OAr′)₃ Pr(OAr′)₃ and Nd(OAr′)₃ crystallize (at approximately 150 K and 200 K, respectively) in the monoclinic space group P2₁ with four molecules in the unit cell. If one considers only the directly coordinating oxygen atoms, the effective crystal field is of C_3v symmetry. The signals in the optical spectra of Pr(OAr′)₃ are broad using either solutions or solids, even at ca. 80‐90 K, thus they are not suitable for interpretation purposes. Nd(OAr′)_3, however, exhibits sharp absorption bands at room and low temperatures, which are assigned in analogy to the previously identified absorption transitions of Nd[N(SiMe₃)₂]₃ based on optical polarization measurements. The thus derived crystal field splitting pattern is simulated by fitting the free parameters of a phenomenological Hamiltonian, achieving a reduced r.m.s. deviation of 26.4 cm^—1 for 64 assignments. The parameters used allow the estimation of the ligand field strength associated with the (OAr′)^— ligand, the insertion of this ligand into empirical nephelauxetic and relativistic nephelauxetic series, and the setup of experimentally‐based non‐relativistic and relativistic molecular orbital schemes in the f range.     

A molecular mechanics study on novel Ln(0) π-arene compounds

To examine the steric effects on the stability of Ln(0) π-arene compounds, molecular mechanics (MMP2) calculations are performed on Gd(η-C₆H₆)₂ and Ln(η-Bu^t₃C₆H₃)₂ (where Ln is Gd, Yb and Y ). The small potential-well depth ( ≈ 2 kcal mol⁻¹) and the large Gd-C equilibrium distance ( > 3.3 Å) explains the instability of Gd(η-C₆H₆)₂, while the difference in the stability between Gd(η-Bu^t₃C₆H₃)₂ and Yb(η-Bu^t₃C₆H₃)₂ can be attributed to the difference in the van der Waalsradii of the two metals and the more contracted 5d orbitals on the Yb atom.     

Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente. 41 Synthese,Kristall‐, Molekül‐ und Elektronenstruktur eines Bis(cyclohexylisonitril)‐Addukts des Grundkörpers Tris(bis(trimethylsilyl)amido)erbium(III) sowie Elektronenstrukturen ausgewählter Monoaddukte

Electronic Structures of Highly Symmetrical Compounds of f Elements. 41 Synthesis, Crystal, Molecular and Electronic Structure of a Bis(cyclohexylisonitrile) Adduct Derived from the Tris(bis(trimethylsilyl)amido)erbium(III) Moiety and Electronic Structures of Selected Mono Adducts The reaction of tris(bis(trimethylsilyl)amido)erbium(III) (Er(btmsa)₃) with two equivalents of cyclohexylisonitrile yields the corresponding bis adduct [Er(btmsa)₃(CNC₆H₁₁)₂] ( 1 ). Complex 1 crystallizes in the monoclinic space group C2/c with a = 2542.9(11) pm, b = 1208.4(4) pm, c = 1783.0(2) pm, β = 122.39(3)°, V = 4.638(5)·10⁹ pm³, Z = 4 and R = 0.0380. The structure of compound 1 features the five coordinate Er³⁺ central ion in a nearly exact trigonal bipyramidal environment, with three btmsa ligands in the equatorial and the two cyclohexylisonitrile molecules in the axial positions. On the basis of the absorption spectra of bis adduct 1 and the mono(tetrahydrofuran) as well as the mono(triphenylphosphine oxide) adducts [Er(btmsa)₃(THF)] ( 2 ) and [Er(btmsa)₃(OPPh₃)] ( 3 ), respectively, the underlying truncated crystal field (CF) splitting patterns of these compounds could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian. Reduced r.m.s. deviations of 13.0 cm^?1 (42 assignments), 16.0 cm^?1 (63 assignments) and 17.5 cm^?1 (55 assignments) could be achieved for compounds 1 , 2 and 3 , respectively. Making use of the phenomenological CF parameters of the fits, the experimentally based non‐relativistic molecular orbital schemes of complexes 1 , 2 and 3 were set up, and compared with that of base‐free Er(btmsa)₃.     

The crystal structure of Tl0.84V5Se8 and magnetic bulk properties

While the antiferromagnetic binary compound V₅Se₈ (Y. Kitaoka and H. Yasuoka, J. Phys. Soc. Jpn.48, 1460, 1980) of which the measured magnetic susceptibility above 27 K cannot be fitted to a Curie-Weiss law and a Curie-Weiss law with a term for the temperature-independent paramagnetism, the ternary compound Tl_0.84V₅Se₈ exhibits paramagnetism. The measured susceptibility fits the equation $\text{χ = χ}{}_0\text{+}\text{C}\text{(T ? θ)}$. In comparison to Tl_0.96V₅S₈ (W. Bensch, E. Amberger, and J. Abart, in press) with shorter VV distances than in Tl_0.84V₅Se₈, the magnetic moment attributed to V(3) in the selenide is markedly higher.