Zur Elektronenstruktur hochsymmetrischer Verbindungen der f-Elemente 44 [1]. Erstmalige parametrische Analyse des Absorptionsspektrums einer Molekülverbindung des trivalenten Urans: Tris[hydrotris(1-pyrazolyl)borato]uran(III) Electronic Structures of Highly Symmetrical Compounds of f Elements 44 [1]. First Parametric Analysis of the Absorption Spectrum of a Molecular Compound of Tervalent Uranium: Tris[hydrotris(1-pyrazolyl)borato]uranium(III)

The absorption spectrum of tris[hydrotris(1-pyrazolyl)borato]uranium(III) (UTp3) was run at room and low temperatures. From the spectra obtained, a truncated crystal field (CF) splitting pattern could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian achieving an r.m.s. deviation of 37.7 cm–1 for 29 assignments. The parameters used allow the insertion of the Tp ligand into empirical spectrochemical, nephelauxetic and relativistic nephelauxetic series of UIII compounds, and the set-up of experimentally based nonrelativistic and relativistic molecular orbital schemes of UTp3 in the f range. Using the wavefunctions and eigenvalues of the fit, the experimentally determined temperature dependence (in the range 1.34–294.4 K) of μ2eff could be reproduced adopting an orbital reduction factor k = 0.99.