ISSN:
1434-1948
Keywords:
Mass spectrometry
;
Clusters
;
Germanium
;
Tin
;
Lead
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Time-of-flight mass-spectrometric investigations show that laser desorption leads to anionic, large clusters of the elements (E) Ge, Sn, and Pb without special gas-phase clustering conditions and additional ionization processes. Ion formation strongly depends on the nature of the starting materials used during desorption experiments. Cluster anions from pure elements E were observed with a maximum of 6 atoms and their relative intensities decreased exponentially with increasing cluster size. Larger clusters are observed if alkali metals (K, Rb, and Cs) are present. Binary phases of nominal composition K4E9, ethylenediamine solutions of these phases, and crystalline compounds containing well-defined cluster anions as in [K([2.2.2]crypt)]3E9 are used as sources for desorption experiments. The latter results in the formation of clusters of 11 (Ge), 15 (Sn), and 13 (Pb) E atoms. Under similar conditions cations are observed at much lower intensities and the maximum cluster size is 6. For E = Ge anions containing two different kinds of atoms KGen- are observed with relatively high abundance for n = 5, 9, and 10; KGe11- and KGe13- are also detected. The results are compared to the formation of clusters in binary alloys. Analogies to structurally characterized Zintl ions Enx- (x = 2, 3, 4) are given. The enhanced formation of cluster anions during the laser desorption process in the presence of electropositive metals indicates a more general application for anion formation in the gas phase.
Type of Medium:
Electronic Resource
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