Crystal Field Strengths, Nephelauxetic Effects, and Experimentally Based Molecular Orbital Schemes (in the f Range) of Selected Cyclopentadienyl Complexes of Samarium(III)

The absorption and luminescence spectra of pseudo (ψ) trigonal planar [Sm(η 5 ‐C 5 H 4 t Bu) 3 ] ( 1 ), low symmetric [Sm(η 5 ‐Cp)(η 3 ‐Tp )(η 2 ‐Tp )] (Cp = η 5 ‐cyclopentadienyl; Tp = hydrotris(3,5‐dimethylpyrazolyl)borato) ( 2 ) as well as ψ trigonal pyramidal [Sm(η 5 ‐C 5 H 4 t Bu) 3 (THF)] ( 3 ), [Sm(η 5 ‐Cp) 3 (THF)] ( 4 ) and [Sm(η 5 ‐Cp) 3 (CNC 6 H 11 )] ( 5 ) have been measured at room and low temperatures. From the spectra obtained, truncated crystal field (CF) splitting patterns of these compounds could be derived, and simulated by fitting the parameters of a phenomenological Hamiltonian. On the basis of the CF parameters used, the global CF strengths experienced by the Sm 3+ central ions of complexes 1 − 5 , as well as the individual CF strength associated with one C 5 H 4 t Bu − ligand are estimated. The obtained Slater parameters F 2 and the spin‐orbit coupling parameters ζ 4f allow the insertion of compounds 1 − 5 into truncated nephelauxetic and relativistic nephelauxetic series. Besides, the experimentally based non‐relativistic and relativistic molecular orbital schemes (in the f range) of complexes 1 and, partly, 3 are set up and compared with the results of quantum chemical model calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)