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

The europium and ytterbium complexes of formula [(C<sub>5</sub>Me<sub>5</sub>)Ln]<sub>2</sub>(μ-η<sup>8</sup>:η<sup>8</sup>-C<sub>8</sub>H<sub>8</sub>) 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. YbI<sub>2</sub>(THF)<sub>2</sub> reacts with KC<sub>5</sub>Me<sub>5</sub> and K<sub>2</sub>C<sub>8</sub>H<sub>8</sub> in THF to form [(C<sub>5</sub>Me<sub>5</sub>)Yb(THF)]<sub>2</sub>(μ-η<sup>8</sup>:η<sup>8</sup>-C<sub>8</sub>H<sub>8</sub>), <b>1</b>, in 80% yield. <b>1</b> can be readily desolvated at 30 °C and 10<sup>-7</sup> Torr to afford [(C<sub>5</sub>Me<sub>5</sub>)Yb]<sub>2</sub>(μ-η<sup>8</sup>:η<sup>8</sup>-C<sub>8</sub>H<sub>8</sub>), <b>2</b>, in 80% yield. <b>2</b> crystallizes from toluene and consists of two divalent [(C<sub>5</sub>Me<sub>5</sub>)Yb]<sup>+</sup> moieties bridged by a (C<sub>8</sub>H<sub>8</sub>)<sup>2-</sup> unit with 159° and 161° (C<sub>5</sub>Me<sub>5</sub> ring centroid)−Yb−(C<sub>8</sub>H<sub>8</sub> ring centroid) angles. [(C<sub>5</sub>Me<sub>5</sub>)Eu(THF)<sub>2</sub>]<sub>2</sub>(μ-η<sup>8</sup>:η<sup>8</sup>-C<sub>8</sub>H<sub>8</sub>), <b>3</b>, can be desolvated at 55 °C and 10<sup>-7</sup> Torr to afford [(C<sub>5</sub>Me<sub>5</sub>)Eu]<sub>2</sub>(μ-η<sup>8</sup>:η<sup>8</sup>-C<sub>8</sub>H<sub>8</sub>), <b>4</b>, in 90% yield. <b>4 </b>crystallizes with a molecule of toluene and has 149.3° and 148.9° (C<sub>5</sub>Me<sub>5</sub> centroid)−Eu−(C<sub>8</sub>H<sub>8</sub> centroid) angles. Complex <b>2</b> reacts with 1,3,5,7-cyclooctatetraene to form (C<sub>5</sub>Me<sub>5</sub>)Yb(C<sub>8</sub>H<sub>8</sub>), <b>5</b>.