By comparing the absorption spectrum of pseudo trigonal planar Sm(eta(5)-C(5)Me(5))(3) (1) (KBr pellet, methylcyclohexane solution) with the previously assigned one of Sm(eta(5)-C(5)Me(4)H)(3) (2) a truncated experimental crystal field (CF) splitting pattern of the former compound could be derived in the NIR range. Because of its dark brown color, fluorescence is not observed from complex 1, and thus the CF splitting pattern in the low energy range could not be determined on the basis of luminescence measurements. However, comparing the FIR and MIR spectra (pellets) as well as the Raman spectra of oriented single crystals of 1 with those of La(eta(5)-C(5)Me(5))(3) (3) at least two additional CF levels could be detected. The free parameters of a phenomenological Hamiltonian were fitted to the thus extended CF splitting pattern of 1, leading to a reduced rms deviation of 15.0 cm(-1) for 21 assignments. On the basis of these phenomenological CF parameters, the global CF strength experienced by the Sm(3+) central ion was estimated, and seems to be the third largest one ever encountered in Sm(III) chemistry. The obtained Slater parameter F(2) and the spin-orbit coupling parameter zeta(4f) allow the insertion of compound 1 into empirical nephelauxetic and relativistic nephelauxetic series, respectively, of Sm(III) compounds. With its low F(2) value, complex 1 is the most covalent Sm(III) compound (considering only f electrons) found to date. The experimentally based non-relativistic molecular orbital scheme (in the f range) of complex 1 was set up and compared with the results of a previous Xalpha-SW calculation on the pseudo trigonal planar model compound Sm(eta(5)-C(5)H(5))(3). In the frame of the search for f-f and electronic Raman transitions, the vibrational spectra (FIR/MIR of pellets, Raman spectra of oriented single crystals) of compound 1 were recorded too, and partly assigned on the basis of the observed coincidences and polarizations.

No abstract

The absorption spectrum of tris[hydrotris(1-pyrazolyl)borato]uranium(III) (UTp 3 ) 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 EinleitungWährend der letzten Jahrzehnte wurden die Kristallfeld(KF)-Aufspaltungsmuster hunderter Festkörper und Salze [2-7] sowie dutzender Molekülverbindungen der trivalenten Lanthaniden (Ln) mit Liganden der Stöchiometrien [η 1 -CH(SiMe 3 ) 2

Electronic Structures of Highly Symmetrical Compounds of f Elements. 40. Parametric Analysis of the Crystal Field Splitting Pattern of Tris(hydrotris(1‐pyrazolyl)borato)neodymium(III) The absorption spectrum of tris(hydrotris(1‐pyrazolyl)borato)neodymium(III) (NdTp3) 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 11.0 cm−1 for 48 assignments. The parameters used allow the estimation of the ligand field strength experienced by the Nd3+ central ion, the insertion of the Tp ligand into empirical nephelauxetic and relativistic nephelauxetic series, and the set‐up of experimentally based nonrelativistic molecular orbital schemes in the f range.

Electronic Structures of Organometallic Complexes of f Elements. 68 Absorption and First Luminescence and Raman Spectroscopic Polarization Measurements of an Oriented Organometallic Single Crystal: Pr(C5Me4H)3 Optical polarization measurements of oriented single crystals of Pr(C5Me4H)3 (1) were performed at room temperature. In order to separate “cold” and “hot” f‐f‐transitions and νC–H combination vibrations, the absorption spectra of KBr pellets of compound 1 and La(C5Me4H)3 (2) were additionally recorded at ca. 77 K. To gather additional information about the wavefunctions of the crystal field (CF) states of complex 1, a magnetic circular dichroism spectrum of 1 was recorded too. From the spectra obtained, a partial CF splitting pattern of 1 was derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian, leading to a reduced r.m.s. deviation of 24.8 cm−1 for 24 assignments. On the basis of these phenomenological CF parameters, the global CF strength experienced by the Pr3+ central ion was estimated, and seems to be the largest one ever encountered in PrIII chemistry. The obtained Slater parameter F2 and the spin‐orbit coupling parameter ζ4f allow the insertion of compound 1 into empirical nephelauxetic and relativistic nephelauxetic series, respectively, of PrIII compounds. With its low F2 value, complex 1 is the most covalent PrIII compound (considering only f electrons) found to date. The experimentally‐based non‐relativistic molecular orbital scheme (in the f range) of complex 1 was determined and compared with the results of a previous Xα‐SW calculation on the ψ trigonal planar model compound Pr(η5‐C5H5)3. In the framework of the search for “polarized” luminescence transitions, polarized Raman spectra of 1 were recorded too, and compared to the corresponding FIR and IR spectra run by means of pellets.