Preparation and characterization of several group 12 element (Zn, Cd)- bis (thiolate) complexes and evaluation of their
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Preparation and characterization of several group 12 element (Zn, Cd)-bis(thiolate) complexes and evaluation of their potential as precursors for 12–16 semiconducting materials William S. Rees, Jr.a) and Gertrud Kr¨auter School of Chemistry and Biochemistry, and School of Materials Science and Engineering and Molecular Design Institute, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 (Received 16 August 1995; accepted 23 May 1996)
Compounds of the general formula M(SR)2 (M Zn, Cd; R i-Pr, t-Bu, Bz) have been prepared and explored as potential unimolecular starting materials for the preparation of binary group 12 metal sulfides. These new compounds have been characterized by IR spectroscopy and thermogravimetric analysis. Chemical derivatization of these insoluble metal-bis(thiolate) compounds by complexation with N-CH3 -imidazole renders them more soluble. These adducts were investigated by elemental analysis. Thermolytic decompositions of both the parent and derivatized compounds have been carried out both in the solid state and by heating a suspension of the appropriate metal-bis(thiolate) compound in an inert high boiling hydrocarbon medium. The thermolysis products have been studied by GC/MS (liquids) and x-ray powder diffraction (XRPD), scanning electron microscopy (SEM), and particle size determination (solids).
I. INTRODUCTION
Along with 13 –15 compound semiconducting electronic materials (e.g., GaAs, InP, etc.), 12 –16 compounds (e.g., Zn, Cd, Hg; S, Se, Te) have attracted significant interest for several years and still are the subject of intense investigation. (IUPAC recommendation for group 1–18 numbering scheme of the Periodic Table. The common U.S. terms are 3–5 (III–V) and 2–6 (II –VI), respectively.) These compounds—among them the sulfides of zinc and cadmium— show interesting electrical and optical properties such as semiconductivity, photoconductivity, and luminescence.1 Cadmium sulfide is highly photosensitive and is employed widely in photoconducting cells, where it can handle power levels up to several watts. Zinc sulfide phosphors are attracting interest due to their luminescence properties.2,3 Zinc sulfide, like zinc oxide, is a piezoelectric material, undergoing distortion of the crystallographic tetrahedron upon application of a shearing stress.4 Recent efforts in this group have focused on the exploration of new routes to and precursors for these materials.5–9 The conventional method for the preparation of binary group 12 element sulfides involves the decomposition of two-component mixtures of volatile organometallic precursors, typically metal alkyls, and H2 S or thiophene.10–13 Although this method leads to the formation of the desired materials, a number of problems persist, including low long-term stability of some current precursor compounds, inhomogeneous a)
Address all correspondence to this author. J. Mater. Res., Vol. 11, No. 12, Dec 1996
multicomponent mixing, and intrinsic high reactivity and toxicity of presently
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