Synthesis, Structure, and Reactivity of Unsolvated Triple-Decked Bent Metallocenes of Divalent Europium and Ytterbium

Abstract

The europium and ytterbium complexes of formula [(C5Me5)Ln]2(μ-η8:η8-C8H8) have been synthesized and structurally characterized to determine the dependence of the (ring centroid)−metal−(ring centroid) angles on the size and electron configuration of the metal. YbI2(THF)2 reacts with KC5Me5 and K2C8H8 in THF to form [(C5Me5)Yb(THF)]2(μ-η8:η8-C8H8), 1, in 80% yield. 1 can be readily desolvated at 30 °C and 10-7 Torr to afford [(C5Me5)Yb]2(μ-η8:η8-C8H8), 2, in 80% yield. 2 crystallizes from toluene and consists of two divalent [(C5Me5)Yb]+ moieties bridged by a (C8H8)2- unit with 159° and 161° (C5Me5 ring centroid)−Yb−(C8H8 ring centroid) angles. [(C5Me5)Eu(THF)2]2(μ-η8:η8-C8H8), 3, can be desolvated at 55 °C and 10-7 Torr to afford [(C5Me5)Eu]2(μ-η8:η8-C8H8), 4, in 90% yield. 4 crystallizes with a molecule of toluene and has 149.3° and 148.9° (C5Me5 centroid)−Eu−(C8H8 centroid) angles. Complex 2 reacts with 1,3,5,7-cyclooctatetraene to form (C5Me5)Yb(C8H8), 5.

“Non‐VSEPR” Structures and Bonding in d0Systems

“…It is unclear how reliable such estimates are. For example, a recently reported bent structure for a triple‐decker sandwich without alkyl substituents at the central C 8 H 8 ring has been taken as evidence against the importance of vdW attractions 176. Even if weak attractive interactions are important, this implies that the other factors involved (covalent bonding, core polarization, ligand repulsion) act together to provide a very shallow bending potential curve,27 such that the weak dispersive forces may become decisive.…”

Nicht-VSEPR-Strukturen und chemische Bindung in d0-Systemen

“…Offensichtlich ist dann die Gröûe der Liganden von besonderer Bedeutung. [176] Selbst wenn schwache anziehende Wechselwirkungen wichtig sind, impliziert dies, dass die anderen beteiligten Faktoren (kovalente Bindung, Rumpfpolarisation, Ligandenabstoûung) so zusammenwirken, dass eine sehr flache Potentialmulde für die Bindungswinkeldeformation entsteht, [27] was letztlich dazu führt, dass die schwachen dispersiven Kräfte entscheidend werden. Während mehrere permethylierte Komplexe des Typs [MCp* 2 ] (M Sm, Eu, Yb, Ba; Cp* h 5 -C 5 (CH 3 ) 5 ) im Festkörper gewinkelte Strukturen aufweisen (potentielle Einflüsse durch intermolekulare Wechselwirkungen sind dabei zu beachten, siehe Abschnitt 2.1), bedingen gröûere Alkylsubstituenten an den Cyclopentadienlyringen aufgrund des sterischen Anspruches der Liganden schlieûlich lineare Metallocenstrukturen.…”

Retraction: Lanthanide–Alkali Metal Sandwich Complexes: Synthesis, Structure, and Solvent‐Mediated Redox Transformations, and One‐Dimensional Frameworks Assembled through Cation–Arene π Interactions

“…Divalent lanthanocenes [(C 5 Me 5 ) 2 Ln] with sandwich structure have attracted considerable attention in the past few decades. [21] Evans et al reported triple-decker bent metallocenes complexes of divalent lanthanides [(m-h 8 [22] Recently, Edelmann et al reported a rare tetradecker sandwich complex of a divalent lanthanide, namely, [(C 5 Me 5 )Yb(m-h 8 [23] Half-sandwich bistetramethylaluminate complexes of the rare earth metals were reported by Anwander et al [24] Complexes with one, (2), Sm1À N2 2.550(2), Si1ÀN1 1.693 (2), Si1ÀN2 1.701 (2), K1ÀO1 2.752 (2), K1À C14 3.222 (3), K1ÀC16 3.077 (3), K1ÀC17 3.094 (3), K1ÀC15 3.114 (3), K1À C18 3.168 (3), K1ÀX1 A 2.829, K1ÀX1B 2.925; N1-Sm1-N1A 180.00 (10), N2-Sm1-N2A 180.00 (9), N1-Sm1-N2 63.32 (7). (2) LnÀN2 2.550 (2) 2.442 (2) Si1ÀN1 1.693 (2) 1.703 (2) Si1ÀN2 1.701 (2) 1.696 (2)…”