Zur Elektronenstruktur metallorganischer Komplexe der f‐Elemente. 65 Erstmalige Beobachtung des linearen Dichroismus bei einem homoleptischen metallorganischen π‐Komplex der f‐Elemente: Tris(η 5 ‐tetramethylcyclopenta‐dienyl)neodym(III)

Electronic Structures of Organometallic Complexes of f Elements. 65 First Observation of Linear Dichroism of a Homoleptic Organometallic π Complex of f Elements: Tris(η 5 ‐tetramethylcyclopentadienyl)neodymium(III) The absorption spectrum of a powder sample of pseudo (Ψ) trigonal planar Nd(η 5 ‐C 5 Me 4 H) 3 ( 1 ) has been measured at room temperature and ca. 40 K, respectively, and the linear dichroism spectra of σ‐ and π‐type of an oriented single crystal at ambient temperature and 77 K. Neglecting the signals of the C–H combination vibrations and overtones extracted from the absorption spectrum of La(η 5 ‐C 5 Me 4 H) 3 ( 2 ), the observed polarization properties of the remaining f‐f transitions allowed the derivation of a truncated crystal field splitting pattern. The free parameters of a phenomenological Hamiltonian were fitted to this pattern leading to a reduced r.m.s. deviation of 16.1 cm −1 for 38 assignments. The temperature dependence of the paramagnetic susceptibility of 1 was calculated, making use of the crystal field energies and wavefunctions of the fit. Introducing an orbital reduction factor of 0.98, calculated values of 1 agree well with the experimental ones of Ψ trigonal planar Nd(C 5 H 4 tBu) 3 .