Bisvinylated [R-Ge₉-Ge₉-R]^4- Cluster Dimers

The syntheses, crystal structures, and NMR and Raman spectroscopic characterization of two compounds with a new member of the organically functionalized dimeric Ge₉-Ge₉ polyanion [R-Ge₉-Ge₉-R]^4- with R = CH=CH₂ are presented. [K([2.2.2]crypt)]₄[(CH₂=CH)-Ge₉-Ge₉-(CH=CH₂)]·1.76 en (1) was synthesized either at elevated temperature by the reaction of K₄Ge₉ and bis(trimethylsilyl)acetylene in ethylenediamine or at ambient temperature in the presence of Pt(PPh₃)₄. [K(18crown-6)]₄[(CH₂=CH)-Ge₉-Ge₉-(CH=CH₂)]·4 en (2) was obtained from the prefabricated monomeric bisvinylated Ge₉ cluster [Ge₉(CH=CH₂)₂]^2- and an ethylenediamine solution of the intermetallic compound K_4.79Co_0.79Sn₉. The reductive cleavage of one or two vinyl groups from [Ge₉(CH=CH₂)₂]^2- - a prerequisite for the latter reaction - could be shown by reacting a solution of the divinylated [Ge₉(CH=CH₂)₂]^2- anion in liquid ammonia with elemental potassium, which resulted in the formation of the ligand-free Ge₉^4- cluster in the new compound [K₅(OH)]Ge₉(NH₃)₁₁ (3).