Die inneren Schwingungen der Tetrahetero-Tetrahedran-Anionen Ge44, Sn44- und Pb44

The Internal Vibration of the Tetrahetero-Tetrahedrane Anions Ge₄^4?, Sn₄⁴-, and Pb₄⁴ The Frequencies of the internal vibrations ν₁ (A₁), ν₂(E), ν₃(T₂) of the tetrahetero-tetrahedrane an ions Ge₄⁴- and Sn₄⁴- are determined from the infrared and Raman spectra of K₇LiGe₈ and KSn, respectively. A comparison of the characteristic vibration of tetrahedrane anions X₄⁴- (X = Si, Ge, Sn)and the isoelectronic neutral tetrahedranes Y₄ of the neighbouring elements (Y = P, As, Sb) shows a rather constant ratio of the corresponding frequencies k = v^?(X₄⁴-) = 0,77. This allows for an estimate of v^?(Pb₄⁴-) from the known Bi₄data. In the inflated spectrum of KPb bands are observed in the predicted frequency range.