Synthesis and Reactivity of Fluorenyl-Based Germanium(II) Compounds.

We present the synthesis of alkyl-substituted germylenes GeFlu 2 , Ge(Flu TMS ) 2 , and Flu TMS GeCl (Flu = 9 H -fluorenyl, Flu TMS = 9-trimethylsilyl-9 H -fluorenyl) using bulky fluorenyl ring systems and modifications of that. GeFlu 2 can only be crystallized as its three-membered ring trimer, whereby the reaction is accompanied by the formation of several byproducts, such as [Li(THF) 4 ][Ge(Ge 3 Flu 7 H)]. These results led to the modification of the fluorenyl framework by substitution the one H atom in the 9-position by a TMS group. With the synthesis of the corresponding Li salt LiFlu TMS , Ge(Flu TMS ) 2 could be isolated in good yields in a further reaction. The homoleptic Ge(Flu TMS ) 2 is found in its crystalline form as a monomer and thus belongs to the series of monomeric alkyl-substituted germylenes. Also, the corresponding monoalkyl-substituted halogenido germylene was isolated as a four-membered ring tetramer [Flu TMS GeCl] 4 during an unselective reaction. However, Flu TMS GeCl undergoes significant stabilization through the formation of the monomeric phosphane adduct Flu TMS GeCl·PEt 3 , which greatly increases the selectivity of the reaction. During further reactions of Ge(Flu TMS ) 2 with a GeBr solution (toluol/ n Pr 3 P), more impressions of the reactivity of Ge(I)X solutions with germylenes were achieved, showing that those germylenes take part in the disproportionation reaction of metastable Ge(I) solutions to give oxidized Ge(IV) compounds like (Flu TMS ) 2 GeBr 2 .