title: The unprecedented tetrakis-(disulfato)-silicate anion [Si(S2O7)4]4-, its germanium congener [Ge(S2O7)4]4-, and the tris-(disulfato)-metallates [M(S2O7)3]2- (M = Si, Ge, Ti), stabilized by divalent counter cations B2+ (B = Sr, Ba, Pb).
abstract: The reaction of oleum (65% SO(3)) with the tetrachlorides of silicon, germanium, and titanium, respectively, led to the complex disulfates Sr(2)[M(S(2)O(7))(4)] (M = Si, Ge), Ba[M(S(2)O(7))(3)] (M = Si, Ge, Ti) and Pb[M(S(2)O(7))(3)] (M = Ge, Ti) if strontium, barium, and lead were used as divalent counter cations. The strontium compounds exhibit the unique tetrakis-(disulfato)-metallate anions [M(S(2)O(7))(4)](4-) with the silicon and germanium atoms in octahedral coordination of two chelating and two monodentate disulfate groups. All of the other compounds display tris-(disulfato)-metallate anions [M(S(2)O(7))(3)](2-) with three chelating disulfate groups surrounding the M atoms. Thermoanalytical investigations on the germanium compounds Sr(2)[Ge(S(2)O(7))(4)] and Ba[Ge(S(2)O(7))(3)] revealed their decomposition in multi-step processes leading to a mixture of BSO(4) and BGe(4)O(9) (B = Sr, Ba), while the thermal degradation of Pb[Ti(S(2)O(7))(3)] yields PbTiO(3). For selected examples, IR data are additionally presented.
authors.affiliation: Carl von Ossietzky University of Oldenburg, Institute of Pure and Applied Chemistry, Carl-von-Ossietzky-Strasse 9-11, 26129 Oldenburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Logemann
authors.forename: Katja
authors.initials: K
authors.lastname: Rieß
authors.forename: Mathias S
authors.initials: MS
authors.lastname: Wickleder