Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente: LI. Synthese, Kristall-, Molekül- und Elektronenstruktur von Cp3Nd(NCCH3)2

Cp3Nd(NCCH3)2 (1) crystallizes in the orthorhombic space group Pbcn with a=13.961(2) Å, b=8.484(2) Å, c=14.840(2) Å, Z=4, R=0.0359, Rw=0.0408 for 1191 data and I>3σ(I). Like in the case of the La, Ce and Pr derivatives the Nd3+ central ion of compound 1 is pseudo trigonal bipyramidally coordinated by three η5-bonded Cp rings in the equatorial plane (Nd–ring centre distances 2.561 Å, 2.554 Å) and two acetonitrile groups in the axial positions (Nd–N=2.764(5) Å). The absorption spectra of extremely sensitive 1 (pellets), the much more stable optically diluted Cp3La0.8Nd0.2(NCCH3)2 (2) (Single crystals), Cp3La(NCCH3)2 (3) (Single crystals) and Cp3Nd·NCCH3 (4) (pellets) were recorded at room and low temperatures. From the spectra obtained, truncated crystal field splitting patterns of complexes 2 and 4 were derived, and simulated by fitting the parameters of an empirical Hamiltonian. For 56 and 55 assignments, respectively, reduced r.m.s. deviations of 32.3 cm−1 and 20.9 cm−1 are achieved for 2 and 4. From the parameters used the experimentally based non-relativistic and relativistic molecular orbital schemes in the f range are set up for 2 and 4. On the basis of the calculated wavefunctions and eigenvalues obtained from the fits, the spectroscopic splitting factors (extracted from the EPR spectrum) of 2 and the temperature dependence of μeff2 of 1 and 4 can be explained. The existence of Cp3La(NCCH3)2:Tb3+ (5) is proved by the luminescence spectrum of this complex.