PREPARATION OF ZNS AND CDS BY THERMAL-DEGRADATION OF (METHANETHIOLATO)ZINC AND (METHANETHIOLATO)CADMIUM COMPLEXES, [M(SME)2]N (M = ZN, CD)

Reactions of aqueous MeSNa with ZnCl2 and with CdCl2 give the methanethiolato complexes [Zn(SMe)2]n (1a) and [Cd(SMe)2]n (2), respectively. Reaction of MeSH with ZnEt2 in hexane also gives [Zn(SMe)2]n (1b). [Zn(SEt)2]n (3) and [Zn(S-i-Pr)2]n (4) are obtained by reaction of EtSLi and i-PrSLi with ZnI2, respectively. Elemental analyses of the complexes give satisfactory results. Peaks in the X-ray diffraction pattern of 1b are considerably broader than those of 1a. Thermolysis of 1a and 1b at 260-degrees-C gives beta-ZnS accompanied by evolution of MeSMe in almost quantitative yields. Thermolysis of 2 under similar conditions give CdS as a mixture of alpha- and beta-forms. Thermogravimetric analyses of the thiolato compounds also suggest elimination of MeSMe in the vicinity of 230-240-degrees-C. TG curves of 1b and 2 at constant temperatures indicate that the thermolysis obeys first-order kinetics in [M(SMe)2]n. Activation parameters of the reactions are 143 and 191 kJ mol-1, respectively. Thermolysis of 1a obeys autocatalytic type kinetics expressed by the kinetic equation in [x/(1 - x)] = kt + C (x: reacted fraction). Heating the (ethanethiolato)zinc complex 3 gives ZnS similarly to the case of 1a, 1b, and 2, while thermolysis of 4 is much slower than the reactions of these complexes.