Alkaline metal stannide-stannates:: 'Double salts' with Zintl Sn44- and stannate SnO34- anions

Using the reduction of tin oxides with the elemental alkaline metals rubidium and cesium, stannide stannates have been synthesized which contain Zintl anions [Sn-4](4-) (i.e. Sn-1) and isolated oxostannate ions [SnO3](4-) (i.e. Sn-1) together with further oxide ions for charge compensation. The crystal structures of the three compounds A(23.6)Sn(7.40)O(13.2) = A23.6[Sn-4][SnO3](3.4)[O](3) (A=Rb 1a: monoclinic, P2(1)/c, a = 2174.2(6), b = 1137.0(6), c = 2373.6(6) pm, beta = 116.11(2)degrees, Z=4, R1 = 0.056; A=Cs 1b: monoclinic, P2(1)/c, a = 2042.6(6), b = 1185.4(3), c 2481.1(7) pm, beta = 97.06(2)degrees, Z=4, R1 =0.075) and Cs48Sn20O21 Cs-48[Sn-4](4)[SnO3](4)[O](7)[O-2] (2 mono-clinic, P2/c, a = 1701.8(3), b = 877.4(2), c = 4556.9(7) pm, beta = 101.47(1)degrees, R1 = 0.093) have been determined on the basis of single crystal data. The transparency of the compounds allowed the recording of raman spectra of the anion [Sn-4](4-). The Sn-119 Moessbauer spectrum of the rubidium compound shows a singulet in good agreement with RbSn, overlapping a doublet caused by Sn2+ in the asymmetrical environment of the strongly electronegative oxygen ligands of SnO34-.