High-Resolution\nX‑ray Photoelectron Spectroscopy\nof Organometallic (C₅H₄SiMe₃)₃Ln^III and [(C₅H₄SiMe₃)₃Ln^II]^1– Complexes\n(Ln = Sm, Eu, Gd, Tb)

Abstract

The\ncapacity of X-ray photoelectron spectroscopy (XPS) to provide\ninformation on the electronic structure of molecular organometallic\ncomplexes of Ln­(II) ions (Ln = lanthanide) has been examined for the\nfirst time. XPS spectra were obtained on the air-sensitive molecular\ntrivalent 4f^<i>n</i> Cp′₃Ln^III complexes (Ln = Sm, Eu, Gd, Tb; Cp′ = C₅H₄SiMe₃) and compared to those of the highly\nreactive divalent complexes, [K­(crypt)]­[Cp′₃Ln^II] (crypt = 2.2.2-cryptand), which have either 4f^<i>n</i>+1 (Sm, Eu) or 4f^<i>n</i>5d¹ electron configurations (Gd, Tb). The Ln 4d, Si 2p, and C\n1s regions of the Ln­(III) and Ln­(II) complexes were identified and\ncompared. The metal 4d peaks of these molecular lanthanide complexes\nwere used diagnostically to compare oxidation states. The valence\nregion of the Gd­(III) and Gd­(II) complexes was also examined with\nXPS and density function theory/random phase approximation (DFT/RPA)\ncalculations, and this led to the tentative assignment of a signal\nfrom the 5d¹ electron consistent with a 4f⁷5d¹ electron configuration for Gd­(II).