Zur Elektronenstruktur hochsymmetrischer Komplexe der Lanthaniden und Actinoiden, I Magnetismus und Schwingungsspektren von Tris(tetraäthylammonium)-hexaisocyanato-ytterbium(III) / The Electronic Structure of Highly-Symmetrical Lanthanide and Actinide Complexes, I Magnetism and Vibrational Spectra of Tris(tetraethylammonium)-hexaisocyanate-ytterbium(III)

Abstract

The results of a combined infrared and Raman-spectroscopic analysis of the compounds [N(C2H5)4]3[Ln(III)(NCO)6] (Ln = Yb, Lu) confirms the assumption that the central ion Ln3+ is octahedrally surrounded by six linear isocyanate ligands. The recently determined temperature dependence of the magnetic susceptibility of the Yb-complex in the range 1.0 < T < 300.2 K is compatible with the crystal field (= CF) splitting pattern: 0 = Ε(Γ6) < Ε(Γ8) < Ε(Γ7) ≪ Ε(Γ'8) < Ε(Γ'7) and a spectroscopic splitting factor |gexp(Γ6)| = 2.576 [i.e. k(tlu) = 0.955]. Using the cubic first-order CF-functions, the energy differences ΔE(Γ8-Γ6) and ΔΕ(Γ7-Γ6) are fixed at 277 ± 10 and 650 ±130 cm-1 respectively. On this basis, the estimated ratio B4°/B6° of the two underlying cubic CF-parameters is discussed in terms of both “electrostatic” and “covalency” effects. This analysis has been used to interpret the paramagnetism of Cs2NaYbCl6 in terms of much larger CF-parameters than previously suggested