Relativistic and Electron-Correlation Effects in the Ground States of Lanthanocenes and Actinocenes

Abstract

[**] Although IUPAC recommends restriction of metallocene nomenclature to cyclopentadienyl complexes, for the sake of simplicity the expressions lanthanocene, actinocene and so on are used in this paper for sandwich complexes of C 8 H 8 .

Cerocene Revisited: The Electronic Structure of and Interconversion Between Ce2(C8H8)3and Ce(C8H8)2

“…55,56 Thus, the 5f 1 electron is destabilized relative to the 4f 1 electron by about 8 eV, i.e., the 4f 1 electron is a core electron, a result that is consistent with the larger relativistic effects on the nuclei with larger values of Z, which destabilizes the 5f and 6d shells. 6,57 One ramification of this is that the energy involved in making M(IV)(cot -2 ) 2 , with a f 0 (e 2u 0 ) (cot -2 ) 2 (e 2u 4 ) configuration requires less energy for thorium than for cerium. In Th(cot) 2 the enthalpy penalty is compensated by transfer of electron density from e 2u 4 and e 2g 4 ligand molecular orbitals to thorium by way of the 6f and 5d atomic orbitals, respectively, so that the charge on thorium is not +4.…”

Are the Ground States of the Later Actinocenes Multiconfigurational? All-Electron Spin−Orbit Coupled CASPT2 Calculations on An(η8-C8H8)2(An = Th, U, Pu, Cm)

“…This occupation, some five times larger than that found in uranocene, bears a striking resemblance to that of cerocene, where the equivalent occupation is 0.216 (and 1.751 for the corresponding π levels). We therefore conclude that, at the SOF level at least, the electronic structure of the plutonocene ground state can be characterized in the same way as that of cerocene, as suggested by Dolg and Fulde, 24 and from the multiconfigurational point of view the metal-dominated a u /b 1u (e 2u ) 5f δ levels are acting as correlating orbitals to the ring based π(e 2u ) levels.…”

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente LXI. Welche Oxidationszahl hat Cer im tiefvioletten 1,1′,4,4′-Tetrakis(trimethylsilyl)cerocen?

“…Kü rzlich berichteten Streitwieser et al ü ber einen neuen Syntheseweg zur Darstellung von Di(p- [8]annulen)cer(IV) (Cerocen) sowie von substituierten Cerocenen der Stöchiometrien Ce IV (C 8 H 7 R) 2 (R = Me, nBu, tBu, tButoxy) und Ce IV [C 8 H 6 (1,4-SiMe 3 ) 2 ] 2 (1) [2]. Die präparierten Komplexe wurden durch ihre Farben, die Lage ihrer Absorptionsmaxima, ihre 1 H-NMR-und Massenspektren charakterisiert.…”

“…Gemäß den Ergebnissen diverser quantenchemischer Rechnungen von Neumann und Fulde [4] sowie von Dolg et al [5][6][7][8] soll bei Cerocen nicht das ursprü nglich aus der Stö chiometrie gefolgerte 4f 0 -System Ce IV , sondern nach Elektronentransfer zwischen dem Oxidationsmittel Ce IV [5] annähernd widerspiegelt.…”