Cyclopentadienyl complexes tris derivatives

Following the synthesis of tris(cyclopentadienyl) lanthanide complexes, the first examples of organolanthanide derivatives, a vast number of organolanthanide it-complexes with cyclopen-tadienyl (Cp), indenyl (Ind), cyclooctatetraenyl (COT), and related substituted derivatives have been prepared and extensively reviewed [3]. Here we will briefly discuss cyclopentadienyl and allyl derivatives as representatives of organolanthanide K-complexes. 

A new development in silsesquioxane ehemistry is the eombination of sil-sesquioxanes with cyclopentadienyl-type ligands. Reeently, several synthetie routes leading to silsesquioxane-tethered fluorene ligands have been developed. The scenario is illustrated in Seheme 47. A straightforward aeeess to the new ligand 140 involves the 1 1 reaction of 2 with 9-triethoxysilylmethylfluorene. Alternatively, the chloromethyl-substituted c/oxo-silsesquioxane derivative 141 can be prepared first and treated subsequently with lithium fluorenide to afford 140. Compound 141 has been used as starting material for the preparation of the trimethylsilyl and tri-methylstannyl derivatives 142 and 143, respeetively, as well as the novel zirconoeene complex 144. When activated with MAO (methylalumoxane), 144 yields an active ethylene polymerization system. 

As noted earlier, the chloride ligand in Cp3 And (An = Th, U, Np) is labile and this feature has facilitated the synthesis of a great many tris(cyclopentadienyl)actinide(IV) alkyl derivatives by metathesis with alkyllithium or Grignard reagents. The properties and reactivity of these complexes have been extensively studied and reviewed. They exhibit remarkable thermal stability. As members of the general class of CpsAnX complexes, they adopt the ubiquitous pseudotetrahedral coordination geometry that was illustrated earlier in (2). 

Tris(cyclopentadienyl) lanthanide complexes can be used as precursors for the synthesis of lanthanide derivatives via a protonolysis reaction (Figure 8.7) [15,16]. The biggest advantage of this method is that it excludes the formation of lanthanide -ate compounds [17],... 

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