Cyclopentadienyl complexes with lanthanoids

The redox transmetallation method is a simple and convenient preparative route. Cp2Hg and cyclopentadienyl complexes of T1(I) are used as a source of cyclopentadienyl ligands [19]. The reactions of dicyclopentadienylmercury are carried out in THF at 0-20 C with 4-5-fold excess of lanthanoid finely divided and activated by mercury chloride. 

The introduction of substituted cyclopentadienyl ligands has only been successful in two instances. Thus, all lanthanoides form tris-(methylcyclopentadienyl)lanthanoide complexes, Ln(C5HI CH3)3, as well as niimerous adducts of them with Lewis bases (28,37 to 4o). Furthermore, lanthanum, praseodymium and neodymium form compoimds of the type Ln(C5Hif-i-C3H7) 3 (4l). With the more bulky ligands, such as the penta-methylcyclopentadienyl- or even the bis(trimethylsilyl)cyclopentadienyl ligand, only the disubstituted derivatives can be obtained. 

Organolanthanoide hydrides (1 11,1 8,215,221), cyclopentadienyl-ytterbium(ll) complexes (190) as well as the cocondensation products of lanthanoides with acetylenic derivatives (137,216,222) catalyze the hydrogenation of olefins and acetylenes. 

This method allows to obtain the compounds with substituted and unsubstituted cyclopentadienyl ligands practically for all lanthanoids, including hardly accessible compounds of early REM [270], and the triflate complex CpLn(0S02CF3)2(THF)3 as well [241]. 

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