Zur Kenntnis der Oxoplatinate Na2PtO2, Na2PtO3, „K2PtO3”︁ und „Rb2PtO3”︁

The oxoplatinates Na₂PtO₂, Na₂PtO₃, ?K₂PtO₃”? and ?Rb₂PtO₃”?. Hitherto unknown Na₂PtO₂ (greyish black) was prepared. Na₂PtO₂ (orthorhombic, D—Immm; a = 4.58₅, b = 3.11₉, c = 9.58₈ Å) is isotypic with Li₂CuO₂. α-Na₂PtO₃ (darkyellow; red as single-crystals) is monoclinic, C—C2/c (a = 5.41₉, b = 9.38₅, c = 10.75₂ Å, β = 99.67°), Li₂SnO₃-type. According to 3-dimensional single crystal data hitherto unknown β-Na₂PtO₃ (red crystals) is an orthorhombic variant of the Li₂SnO₃-type (a = 18.83₈, b = 6.28₂, c = 9.06₂ Å, Z = 16, D—Fddd; parameters see text); R = 0.080₉, R' = 0.094₈ [256 reflexes (hk0—hk6)]. The Madelung part of the lattice energy (MAPLE) is calculated and discussed for α-, β-Na₂PtO₃, α- and β-PtO₂. For the first time we got K₂PtO₃ and Rb₂PtO₃.     

Die Kristallstruktur des „Thalliumdichlorids,TlCl2”︁

The Crystal Structure of Thallium Dichloride, TlCl₂ Thallium dichloride, TlCl₂, crystallizes tetragonal in the I4₁/a space group with cell constants a = 696.45(8) pm and c = 1 552.8(3) pm. The structure is of the CaWO₄ type so that the compound must be formulated as thallium(I)-tetrachlorothallate(III).     

“Complex” versus “free radical” mechanism for the catalytic decomposition of H2O2 by ferric ions

Kinetic and spectrophotometric measurements made during the Fe³⁺ ion catalyzed decomposition of H₂O₂ have been analyzed using the computer simulation method. Improved values of the rate constants of the “complex scheme” and of the molar absorptivities ofthe intermediates were obtained: k₃/K_M = 4.94 M^?1 min^?1, k₄ = 193 M^?1 min^?1, ε_I/K_M = 52.3 M^?2 cm^?1, ε_II = 25.7 M^?1 cm^?1. The simulation revealed details of the reaction which were unavailable by other means and which explained several features of its kinetics. The total amount of O₂ evolved in the reaction using [H₂O₂] ～ 10^?2 M has been calculated and found to be nearly stoichiometric. O₂ evolution experiments in this region cannot, thus, distinguish between the “complex mechanism” predicting nearly stoichiometric evolution of O₂ and the “free radical mechanism” predicting exactly stoichiometricamounts of O₂. There are discrepancies within the “free radical scheme” with regard to the correct values of the rate constants to fit the reactions of H₂O₂ both with Fe²⁺ and Fe³⁺ ions, as well as other reactions assumed to proceed via free radicals.     

Gasförmiges „H3PS2”︁ – Erzeugung und Charakterisierung

Gaseous “H₃PS₂” – Generation and Characterization Double alkene elimination from molecular ions (El: 70 eV) of dialkyldithiophosphinic acids R₂P(S)SH (R: Et, nPr, nBu) leads to radical cations of composition [H₃PS₂]^+. (m/z 98). By analysis of the collisional activation (CA) mass spectrum and using thermochemical data it was shown that [H₃PS₂]^+. exists as a mixture of structures [H? P(SH)₂]^+. and [HSP? SH₂]^+. containing tri- or dicoordinated phosphorus, respectively. No structure corresponding to ionized dithiophosphinic acid H₂P(S)SH was observed. Via neutralization reionization mass spectrometry (NRMS) neutral molecules ?H₃PS₂”? were obtained which proved to be stable in the dilute gas phase and most probably are of structure H? P(SH)₂. Experimental findings are in accordance with the results of semiempirical MO-calculations (MNDO).