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)(mu-eta(8):eta(8)-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)(mu-eta(8):eta(8)-C8H8), 1, in 80% yield. 1 can be readily desolvated at 30 degrees C and 10(-7) Torr to afford [(C6Me5)Yb](2)(mu-eta(8):eta(8)-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 degrees and 161 degrees (C5Me5 ring centroid)-Yb-(C8H8 ring centroid) angles. [(C5Me5)Eu(THF)(2)](2)(mu-eta(8):eta(8)-C8H8), 3, can be desolvated at 55 degrees C and 10(-7) Torr to afford [(C5Me5)Eu](2)(mu-eta(8):eta(8)-C8H8), 4, in 90% yield. 4 crystallizes with a molecule of toluene and has 149.3 degrees and 148.9 degrees (C5Me5 centroid)-Eu-(C8H8 centroid) angles. Complex 2 reacts with 1,3,5,7-cyclooctatetraene to form (C5Me5)Yb(C8H8), 5.