Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente LIX. Spektrochemische und nephelauxetische Effekte sowie experimentorientierte MO-Schemata (im f-Bereich) pseudo-trigonal-planarer (substituierter) Tris(η5-cyclopentadienyl)neodym(III)-Kompl

The absorption spectra of pseudo (ψ) trigonal planar Nd( η5-C5H4tBu)3 (1) and Nd(η5-C5H4SiMe3)3 (2) as well as ψ trigonal pyramidal [Nd(η5-C5H4tBu)3(THF)] (3) have been measured at room and low temperatures.From the spectra obtained, truncated crystal field (CF) splitting patterns of these compounds could be derived, and simulated by fitting the parameters of a phenomenological Hamiltonian.For 60, 57 and 74 assignments, reduced r.m.s.deviations of 24.7, 23.1 and 29.0 cm−1 were achieved for complexes 1–3, respectively.On the basis of the CF parameters used, the global CF strengths experienced by the Nd3+ central ions of complexes 1–3, as well as the individual CF strengths associated with one [C5H4tBu]− or [C5H4SiMe3]− ligand, respectively, of homoleptic compounds 1 and 2 are estimated.The obtained Slater parameters F2 and the spin–orbit coupling parameters ζ4f allow the insertion of compounds 1–3 into truncated nephelauxetic and relativistic nephelauxetic series.Whereas adduct 3 exhibits a pronouncedly lower global ligand field strength as well as increased F2 and ζ4f values, the compounds 1 und 2 show (within experimental error) nearly identical values.Besides, the experimentally-based non-relativistic and relativistic molecular orbital schemes (in the f range) of complexes 1 and 3 are set up and compared with the as yet available results of quantum chemical model calculations.