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

The europium and ytterbium complexes of formula [(C5Me5)Ln]2(μ-η88-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-η88-C8H8), 1, in 80% yield. 1 can be readily desolvated at 30 °C and 10-7 Torr to afford [(C5Me5)Yb]2(μ-η88-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-η88-C8H8), 3, can be desolvated at 55 °C and 10-7 Torr to afford [(C5Me5)Eu]2(μ-η88-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.