Electronic structures of organometallic complexes of f elements LXXIII: Parametric analysis of the crystal field splitting pattern of tris(η5-pentamethylcyclopentadienyl)cerium(III)

By comparing the far infrared (polyethylene pellets, room temperature) and mid-infrared spectra (KBr pellets, room temperature and ca. 90 K) of pseudo trigonal planar Ce(eta(5)-C5Me5) 3 (1) with the corresponding ones of La(eta(5)-C5Me5)(3) (2) and considering the low temperature paramagnetic susceptibility data of 1 the crystal field (CF) splitting pattern of 1 could be derived. The free parameters of a phenomenological Hamiltonian were fitted to this pattern achieving an r.m.s. deviation of 8.9 cm (1) for seven assignments. The fact that the difference of the experimental energies of the barycenters of CF levels of the multiplets F-2(7/2) and F-2(5/2) is larger than in the gaseous free Ce3+ ion (experimental "anti"-relativistic nephelauxetic effect) could be explained by coupling effects of these multiplets via the CF, resulting in a lower spin-orbit coupling parameter than in the case of the free gaseous Ce3+ ion. The experimental CF splitting pattern of 1 is compared to the results of a relativistic DV-X alpha calculation on the pseudo trigonal planar model compound Ce(eta(5)-C5H5)(3). In addition, the prediction of the energies of f -> d and charge transfer transitions of Ce(eta(5)-C5H5)(3) are compared to the absorption and luminescence spectra of complex 1. (C) 2010 Elsevier B.V. All rights reserved.