Ligand Exchange Processes in Tetraalkoxytelluranes

Hugo E. Gottlieb, Shmaryahu Hoz, Iris Elyashiv, Michael Albeck

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15 Scopus citations


Alkoxy groups in acyclic tetraalkoxytelluranes interchange quickly on the NMR time scale at room temperature, both intramolecularly (axial/equatorial positional interconversion) and intermolecularly (the reaction between telluranes and free alcohols). In the latter case, no thermodynamic preference is found for the binding of simple primary or secondary alcohols, but tert-butyl alcohol is significantly less favored as a ligand. The 125Te NMR signals for Te(OEt)4 and Te(OiPr)4 are shown to be broad and very solvent- and concentration-dependent, probably due to associative processes in solution. In contrast, cyclic telluranes such as Te(OCH2CH2O); and Te(OCMe2CMe2O)2 are thermodynamically favored and give sharper 125Te lines. For the latter substance, three ligand reorganization processes were defined and measured by NMR line-shape analysis: (a) a low-barrier (ΔG = 7.0 kcal/mol) axial/equatorial interchange (such as a Berry pseudorotation) that still leaves two distinct methyl signals in the spectrum; (b) a high-barrier (ΔG = 20.9 kcal/mol) mechanism that averages all the methyl groups in the molecule to one line; (c) an acid-catalyzed process, probably involving tellurium inversion, that has the same result as process b.

Original languageEnglish
Pages (from-to)808-811
Number of pages4
JournalInorganic Chemistry
Issue number4
StatePublished - 1 Feb 1994


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