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Érd, Hungary

Kotai L.,Hungarian Academy of Sciences | Kotai L.,Deuton X Ltd. | Sajo I.E.,Hungarian Academy of Sciences | Jakab E.,Hungarian Academy of Sciences | And 11 more authors.
Zeitschrift fur Anorganische und Allgemeine Chemie | Year: 2012

[Tetraamminecadmium(II)] bis(permanganate) (1) was prepared and its crystal structure was elucidated with XRD-Rietveld refinement and vibrational spectroscopic methods. Compound 1 has a cubic lattice consisting of a 3D hydrogen-bonded network built as four by four distorted tetrahedral blocks of [Cd(NH 3) 4] 2+ cations and MnO 4 - anions, respectively. The other four permanganate ions are located in a crystallographically different environment, placed in the cavities formed by the attachment of the building blocks. A low-temperature (≈100 °C) solid phase quasi-intramolecular redox reaction producing ammonium nitrate and amorphous CdMn 2O 4 could be established. Neither solid phase nor aqueous solution phase thermal deammoniation of compound 1 can be used to prepare Cd(MnO 4) 2 and [Cd(NH 3) 2(MnO 4) 2]. During deammoniation of compound 1 in aqueous solution a precipitate consisting of Cd(OH) 2 forms. Additionally, solid MnO 2 and ammonium permanganate (NH 4MnO 4) forms. The solid phase deammoniation reaction (toluene used as heat convecting medium) with subsequent aqueous leaching of the ammonium nitrate formed has proved to be an easy and convenient technique for the synthesis of amorphous CdMn 2O 4+x type NO x and MeSH sensor precursors. The 1-D perdeuterated complex was also synthesized to distinguish the N-H(D) and O-H(D) fragment signals in the TG-MS spectra and to elucidate the vibrational characteristics of the overlapping Mn-O and Cd-N frequencies. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Kotai L.,Hungarian Academy of Sciences | Kotai L.,Deuton X Ltd. | Balint S.,Hungarian Academy of Sciences | Gacs I.,Hungarian Academy of Sciences | And 3 more authors.
Zeitschrift fur Anorganische und Allgemeine Chemie | Year: 2012

The minimal occupancy level (θ min) of the clathrate lattice of gas molecules is defined as the number of guest molecules in the host clathrate lattice, which can stabilize the thermodynamically unstable empty cage by covering the energy demand of the transformation of hexagonal ice into empty clathrate lattice (ΔH trans). The θ min values for chlorine hydrate were determined from the n = f(p) T=const. relationship and the average molar intercalation heat of chlorine in the type I clathrate lattice was also calculated for both type of cavities. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Kotai L.,Hungarian Academy of Sciences | Kotai L.,Deuton X Ltd. | Balint S.,Hungarian Academy of Sciences | Gacs I.,Hungarian Academy of Sciences | And 3 more authors.
Zeitschrift fur Anorganische und Allgemeine Chemie | Year: 2012

A simple and generalized method for calculating the composition of the Type I clathrate gas hydrates is discussed. It is suggested that the use of additive terms in the known temperature dependent molar volume values of hexagonal ice is useful in calculating the molar volume of the empty clathrate cage. Since the molecular weight of the gas hydrate is dependent on the occupation, the degree of occupation can be expressed by using the experimental density values of each hydrate. The results so obtained are in fair agreement with the results calculated from experimental density and X-ray lattice constants, and with the values of the experimentally measured compositions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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