[(C5Me5)Yb(μ-η8,η8-cot)Yb(μ-η8,η8-cot)Yb(C5Me5)] - A Unique Tetradecker Sandwich Complex of a Divalent Lanthanide

摘要

Since its discovery in 1984 the unsolvated divalent lanthanide metallocene [(C5Me5)2Sm] continues to hold great fascination.[1] It has been the subject of theoretical studies aiming to rationalize why the C5Me5 ligands in [(C5Me5)2Ln] (Ln=Sm, Eu, Yb) adopt a bent geometry instead of the sterically more favorable structure with parallel rings.[2] Evidence was found for both valence and metal-core electron participation in the bending process.[3] Moreover, [(C5Me5)2Ln] complexes display an exceptionally high and unique reactivity towards a large variety of reagents.[4] Among the most prominent examples are the formation of [(-N2){Sm(C5Me5)2}2], the first dinitrogen complex of an f element,[5] the trimerization of carbon monoxide,[6] and the preparation of heterobimetallic [(C5Me5)2LnAl(C5Me5)].[7]