Regio- and stereo-specific electrophilic addition of TeBr₄ and ArylTeBr₃ across terminal acetylene bonds

Despite their unique electronic properties and scope for use in applications including semiconductors, catalysis, materials science and medicine, organotellurium compounds remain underexplored. Hence, electrophilic addition reactions of TeBr₄, C₆H₅TeBr₃, 4-MeOC₆H₄TeBr₃ and 1-C₁₀H₇TeBr₃ with terminal acetylene bonds of RC[triple bond, length as m-dash]CH (R = Me₃C, C₆H₅, 4-MeC₆H₄) were performed, producing the respective (Z)-isomer of organotellurium(iv) derivatives [t-BuC(Br)[double bond, length as m-dash]CH]₂TeBr₂ (1), [(C₆H₅)-{t-BuC(Br)[double bond, length as m-dash]CH}]TeBr₂ (2), [(4-MeOC₆H₄)-{t-Bu(C(Br)[double bond, length as m-dash]CH)}]TeBr₂ (3), [(1-C₁₀H₇)-{t-BuC(Br)[double bond, length as m-dash]CH}]TeBr₂ (4), [(4-MeOC₆H₄)-{C₆H₅C(Br)[double bond, length as m-dash]CH}]TeBr₂ (5), [(1-C₁₀H₇)-{C₆H₅C(Br)[double bond, length as m-dash]CH}]TeBr₂ (6), [(C₆H₅)-{4-MeC₆H₄C(Br)[double bond, length as m-dash]CH}]TeBr₂ (7), [(4-MeOC₆H₄)-{4-MeC₆H₄C(Br)[double bond, length as m-dash]CH}]TeBr₂ (8) and [(1-C₁₀H₇)-{4-CH₃-C₆H₄C(Br)[double bond, length as m-dash]CH}]TeBr₂ (9) in good yield. These derivatives were characterized by elemental analysis, ¹H, ¹³C{¹H} and ¹²⁵Te{¹H} NMR spectroscopic techniques. ¹H NMR chemical shifts of the signals due to vinyl protons of compounds 1-4 are shifted ∼0.4 ppm up field due to the electronic effect of t-Bu group. Only one ¹²⁵Te NMR signal is observed for all the derivatives. Among these compounds, 2 and 7 were also characterized by single crystal X-ray studies. The Br atom of the organotellurium(iv) derivatives is invariably involved, at least in the solid state through nonbonding and hydrogen bonding interactions. An intermolecular Te⋯Br nonbonding interaction gives rise to zero-dimensional supramolecular dimeric unit in the crystal lattice of 2 and 7.