A Series of Cyclopentadienyl Lanthanum Complexes with Metalloid Germanium Clusters.

A series of cyclopentadienyllanthanum complexes with the disilylated metalloid germanium cluster [Ge 9 (Hyp) 2 ] 2- [Hyp = Si(SiMe 3 ) 3 ] has been prepared and fully characterized. The synthetic procedure is based on the salt metathesis reaction of two different cyclopentadienyllanthanum diiodides CpLaI 2 (Cp: Cp*, pentamethylcyclopentadienyl; Cp ttt , 1,2,4-tri- tert -butylcyclopentadienyl) with K 2 [Ge 9 (Hyp) 2 ] in tetrahydrofuran (THF) with a subsequent extraction with n -hexane. The composition of the obtained compounds and the mode of coordination of the germanium cluster to the rare-earth metal are strongly influenced by the steric demand of the cyclopentadienyl ligands and the crystallization conditions. The centrosymmetric dimeric compounds with the common formula [CpLa(solv)(η 2,3 -Ge 9 (Hyp) 2 )] 2 [ 1 , Cp = Cp*, solv-THF; 2 , Cp = Cp ttt , solv-NCCH 2 C(Me)NSiMe 3 ] have been isolated by the slow evaporation of a n -hexane solution, while a mononuclear complex [Cp ttt La(THF) 2 (η 3 -Ge 9 (Hyp) 2 )] ( 4 ) was found by crystallization from THF. The repeated recrystallization of 1 from n -hexane afforded the asymmetric dimer [Cp*La(THF)(η 2,3 -Ge 9 (Hyp) 2 )][Cp*La(η 2,3 -Ge 9 (Hyp) 2 )] ( 3 ) with only one coordinated THF molecule.