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)

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–1for 29 assignments. The parameters used allow the insertion of the Tp ligand into empirical spectrochemical, nephelauxetic and relativistic nephelauxetic series of UIIIcompounds, and the set‐up of experimentally based nonrelativistic and relativistic molecular orbital schemes of UTp3in 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 μ2effcould be reproduced adopting an orbital reduction factor k = 0.99.