title: Synthesis, molecular, and electronic structure of (eta(8)-C8H8)Ln(scorpionate) half-sandwich complexes: an experimental key to a better understanding of f-element-cyclooctatetraenyl bonding.
abstract: Synthetic routes leading to two series of (eta(8)-cyclooctatetraenyl)lanthanide(III) scorpionate "mixed sandwich" complexes are reported. The early lanthanide derivatives (COT)Ln(Tp) (Ln = Ce (1), Pr (2), Nd (3), Sm (4)) and (COT)Ln(Tp(Me2)) (Ln = Ce (5), Pr (6), Nd (7), Sm (8)) (COT = eta(8)-cyclooctatetraenyl, Tp = hydrotris(pyrazolyl)borate, Tp(Me2) = hydrotris(3,5-dimethylpyrazolyl)borate) were obtained by reacting the dimeric halide precursors [(COT)Ln(mu-Cl)(THF)]2 with K[Tp] or K[Tp(Me2)], respectively For the late lanthanide elements a different synthetic route was developed. The complexes (COT)Ln(Tp) (Ln = Er (9), Lu (10)) were made by the reaction of (Tp)LnCl2(THF)1.5 with equivalent amounts of K2C8H8. All new compounds were isolated as intensely colored crystalline materials and fully characterized by elemental analyses and spectroscopic methods. The molecular structures of 4, 5, and 8 were elucidated by X-ray diffraction. The optical spectra of compounds 2 and 4-8 were run at room and low temperatures. From the spectra obtained, the underlying crystal field splitting patterns of complexes 2, 4, 6, and 7 were derived and simulated by fitting the free parameters of a phenomenological Hamiltonian. The parameters used allow the estimation of the crystal field strengths experienced by the Ln3+ central ions and the insertion of complexes 2, 4, 6, and 7 into empiric nephelauxetic and relativistic nephelauxetic series. Besides, the experimentally oriented non-relativistic and relativistic molecular orbital schemes of compound 6 were set up and compared with the results of previous model calculations on [Ln(COT)2]-, Pa(COT)2, and U(COT)2.
authors.affiliation: Institut für Anorganische and Angewandte Chemie der Universität Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany.
authors.forename: Hanns-Dieter
authors.initials: HD
authors.lastname: Amberger
authors.forename: Frank T
authors.initials: FT
authors.lastname: Edelmann
authors.forename: Jochen
authors.initials: J
authors.lastname: Gottfriedsen
authors.forename: Regine
authors.initials: R
authors.lastname: Herbst-Irmer
authors.forename: Stefan
authors.initials: S
authors.lastname: Jank
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kilimann
authors.forename: Mathias
authors.initials: M
authors.lastname: Noltemeyer
authors.forename: Hauke
authors.initials: H
authors.lastname: Reddmann
authors.forename: Martina
authors.initials: M
authors.lastname: Schäfer