The <i>closo</i>-Ge₅^2- Anion: Synthesis, Crystal Structure, and Raman Spectrum of (2,2,2-crypt-K⁺)₂Ge₅^2-·THF

The isolation and structural characterization of the closo-Ge52- cluster anion by X-ray crystallography and Raman spectroscopy is reported, completing the series of five-atom homopolyatomic anions of the group 14 elements, M52- (M = Ge, Sn, Pb). The closo-Ge52- anion was obtained as the (2,2,2-crypt-K+)2Ge52-·THF salt which crystallizes in the triclinic system, space group P1, in a unit cell of dimensions a = 10.9657(4) Å, b = 12.1750(5) Å, c = 12.9142(5) Å, α = 62.163(1)°, β = 67.776(1)°, and γ = 84.187(1)°. The trigonal bipyramidal geometry observed for the Ge52- anion (∼D3h point symmetry) is in accord with that predicted by Wade's rules for a 2n + 2 skeletal electron system and has been observed for the Sn52- and Pb52- homologues and for the isovalent Tl57- and Bi53+ ions. The Raman spectrum of the Ge52- anion is compared and assigned by analogy with that of the Bi53+ cation.