Preparation and Characterization of Group 12 Thiolate Complexes and Evaluation of Their Potential as Precursors for II-V
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PREPARATION AND CHARACTERIZATION OF GROUP 12 THIOLATE COMPLEXES AND EVALUATION OF THEIR POTENTIAL AS PRECURSORS FOR II-VI SEMICONDUCTORS
WILLIAM S. REES, JR.*,t,§, GERTRUD KRAUTERt,§ AND VIRGIL L. GOEDKENt Department of Chemistryt, Materials Research and Technology Center§, Florida State University, Tallahassee, FL 32306-3006
ABSTRACT We have prepared compounds having the general formula M(SR) 2 (M = Zn, Cd; R = i-Pr, t-Bu, Bz) and Hg(SR)CI (R = i-Pr, Bz) and investigated their use as potential sources in the preparation of metal sulfides from molecular precursors. Selected examples of the prepared compounds have been studied by single crystal x-ray diffraction. Decomposition has been carried out both in the solid state and by heating a suspension of a metal thiolate in a high boiling hydrocarbon. The decomposition products have been studied by GC/MS (liquids) and XRD (solids).
BACKROUND Molecular compounds have been found to be useful precursors in the preparation of bulk solid state materials. 1 For example, metal alkoxides are widely used to deposit metal oxides 2 and the decomposition of metal thiolates leads in many cases to the formation of metal sulfides. 3 Unfortunately, metal thiolates usually have polymeric structures leading to their insolubility in organic solvents. 4 Therefore, their recrystallization, which is a nescessary step to obtain pure precursor materials, is quite difficult. We have focussed our research efforts on attempts to form soluble metal thiolate complexes both by incorporporation of bulky alkyl substituents and the formation of soluble adducts in the presence of Lewis bases.
Mat. Res. Soc. Symp. Proc. Vol. 283. 01993 Materials Research Society
860
RESULTS AND DISCUSSION The TGA-data of the prepared zinc- and cadmium thiolates suggest that these compounds are converted into metal sulfides under relatively mild conditions (Figure 1). Cubic ZnS is formed during the decomposition of zinc thiolates. Cd(S-i-Pr)2and Cd(S-t-Bu)2 yield hexagonal CdS (Figure 2), while cubic CdS is formed when Cd(S-Bz) 2 is decomposed (Figure 3). GC-MS data of the volatile decomposition products show that dialkyl sulfides are the only observed byproducts of the thermolyses. Decomposition also occurs when a suspension of metal thiolate in decalin is refluxed for 2 days. The as-prepared zincand cadmium thiolates are insoluble in organic solvents. However, they dissolve readily when 1-methylimidazole is added to a suspension of a metal thiolate in toluene. The formed adducts lose 1methylimidazole when heated to 100 0C, and subsequently further decompose forming metal sulfides when the temperature is increased (Figure 4). The prepared mercury thiolato complexes are soluble in polar organic solvents. CI-Hg-S-Bz dissolves in tetramethylethylenediamine (TMEDA) and crystallizes as a monomeric TMEDAadduct (Figure 5). If the unsolvated compound is heated to 2001C benzyl chloride and black mercury sulfide are formed. The black HgS slowly is converted into the more stable orange HgS (cinnabar). We have refined the st
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