| Alkyl acetylenyl tellurides, RC≡CTeR′, where R = n-C4H9, n-C 6H13, n-C10H21, C 6H5, and R′ = CH3, CH(CH 3)2, cyclo-C6H11, CH2CH(CH3)2, CH2(CH2) 6CH3, CH2(CH2)10CH 3, CH2CH2CH(Br)CH3, CH2C 6H5, CH2C6H4-4-NO2 , CH2CH2C6H5 and CH 2CH2OC6H5, have been prepared in excellent yields by the anaerobic reaction of lithium acetylenyl tellurolate with the appropriate alkyl halides in the absence of light. While most of these reactions have been performed at −5 to −10°C the reaction with cyclo-hexyl halide has been conducted at lower temperature (−30°C). Alkyl chloro, bromo and iodo derivatives have provided the same products in the same yields.; The 1H NMR spectra of alkyl acetylenyl tellurides display deshielded resonances for the CHx (x = 1, 2, 3) group directly bound to tellurium. In many cases, specific couplings between tellurium and hydrogen are observed around these resonances. Characteristic features in the 13C NMR spectra include a shielding effect of the sp 3 and sp carbons directly bound to tellurium, and a deshielding effect to the other sp carbon. Closer analysis of the 13C{lcub} 1H{rcub} NMR spectra reveals satellites due to coupling with tellurium. Nuclear magnetic resonances measurements of the 125Te nucleus show a correlation of 125Te chemical shift to the alkyl group of RC≡CTeR′. Our extensive 125Te-NMR study of alkyl acetylenyl tellurides will allow the identification of unknown acetylenyl tellurides. In addition, the 125Te-NMR spectra show a splitting of the 125Te nuclear magnetic resonances due to coupling through up to three bonds with 1H nuclei. Our work provides a considerable amount of data on coupling constants between proton or carbon and tellurium nuclei, for which information in the literature is sparse.; The potential of alkyl acetylenyl tellurides as precursors for the deposition of telluride thin films has been studied. They exhibit a different behavior than diethyl telluride during thermal decomposition. They release elemental tellurium upon decomposition but the mechanism of their decomposition does not appear to go through the same process. Thus the use of diethyl telluride as a precursor leads to the growth of tin telluride films on tin oxide substrates and gold telluride films on gold substrate, while the use of acetylenyl tellurides as precursor does not. This work is the first evidence of formation of metal chalcogenide films by exposure of metal oxide layers to diethyl chalocogenide. (Abstract shortened by UMI.)... |
