Cyclopentadienyl lanthanide Complexes from the Metallic Elements

(ti -CYCLOPENTADIENYL)LANTHANIDE complexes FROM THE METALLIC ELEMENTS 

Submitted by GLEN B. DEACON, GEOFF N. PAIN, and TRAN D. TUONG Checked by WILLIAM J. EVANS/ KEITH R. LEVAN/ and RAUL DOMINGUEZ  

Tris(i/5-cyclopentadienyl)lanthanides were the first authentic organolanth-anides to be prepared1 and bis(t/5-cyclopentadienyl)lanthanide(II) compounds have played a germinal part in the development of lower oxidation state organolanthanide chemistry.2 These cyclopentadienyls are sources of coordination compounds of structural interest and are reagents for the synthesis of other organolanthanides, for example, bis- and mono(t)5-cyclopentadienyl)lanthanide(III) derivatives.2 

In the following sections we detail transmetalation syntheses from ( /5-C5H5)T1 (see Ref. 12) of three (i/5-cyclopentadienyl)lanthanide complexes, which can be isolated analytically pure in nearly quantitative yields simply by evaporation of the filtered reaction solvent. These simplify and optimize our reported syntheses.6,7 

Lanthanide metals were obtained from Research Chemicals as powders. The metals can be weighed and stored in air, but for long term storage, especially of neodymium, use of a dry box is recommended. 

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Fig. 1. Apparatus for the preparation of ( 5-cyclopentadienyl)lanthanide complexes from the metallic elements. 

We can visualise the capability of suitable lanthanide (Ln) compounds (J, 6), e.g. as homogeneous catalysts with respect to olefins, by invoking similar intermediates. Although the series of reportedly catalytically active Ln-complexes spans from the pure trihalide via tris(B-diketonato)complexes to the organo-metallic tris(cyclopentadienyl) and tetra(allyl)complexes (8), respectively, no really optimal combination of ligands on a Ln-element has been found so far. Promising aspects are, however, based on some evidence for "reaction steering" in that either cis- or trans-polybutadienes can be obtained from 1,3-dienes, and either polymers or metathesis products from monoolefins, respectively (Table I). 

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