Liquid ammonia lanthanoids

Ytterbium tends to be more reactive than other lanthanoid elements. It is usually stored in sealed containers to keep it from reacting with oxygen in the air. It also reacts slowly with water and more rapidly with acids and liquid ammonia. 

In I96U, the blue solution of metallic europium in liquid ammonia was found to react with cyclopentadiene. The sublimation of the crude product at U00 C in vacuo yields an ammonia-free syndwich complex, as the first organometallic compound of a lanthanoide in the oxidation state Ln (183). The ytterbiinn complex has been prepared in a similar manner (15) ... 

The first compounds of this series, Cp2Eu and Cp2Yb, have been obtained in the reaction of cyclopentadiene with lanthanoid metals in liquid ammonia [11, 12] ... 

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