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(C 2 H 5 ) 4 ] 3 [Ln(III)(NCO) 6 ] (Ln = Yb, Lu) confirms the assumption that the central ion Ln 3+ 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(Γ 6 ) < Ε(Γ 8 ) < Ε(Γ 7 ) ≪ Ε(Γ' 8 ) < Ε(Γ' 7 ) and a spectroscopic splitting factor |g exp (Γ 6 )| = 2.576 [i.e. k(t lu ) = 0.955]. Using the cubic first-order CF-functions, the energy differences ΔE(Γ 8 -Γ 6 ) and ΔΕ(Γ 7 -Γ 6 ) are fixed at 277 ± 10 and 650 ±130 cm -1 respectively. On this basis, the estimated ratio B 4 °/B 6 ° 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 Cs 2 NaYbCl 6 in terms of much larger CF-parameters than previously suggested