Observation of Te center dot center dot center dot pi and X center dot center dot center dot X bonding in para-substituted diphenyltellurium dihalides, (p-Me2NC6H4)(p-(YCH4)-H-6)TeX2 (X = Cl, Br, I; Y=H, EtO, Me2N)

The supramolecular association of the previously described para-dimethylaminophenyl-substituted diorganotellurium dihalides (p-Me2NC6H4)(2)TeX2 (X = Cl ( 1), Br ( 2), I ( 3)) and (p-Me2NC6H4) RTeCl2 (R= Ph ( 4), p-EtOC6H4 ( 5)), was investigated by X-ray crystallography. Unlike almost all other structurally characterized diorganotellurium dihalides, (p-Me2NC6H4)(2)TeX2 (X = Cl ( 1), Br ( 2), I ( 3)) reveal no secondary Te ... X interactions, but X ... X interactions. The structure of (p-Me2NC6H4) PhTeCl2 ( 4) resembles that of Ph2TeCl2 and shows one secondary Te ... Cl contact, whereas (p-Me2NC6H4)(p-EtOC6H4) TeCl2 ( 5) exhibits neither secondary Te ... Cl nor Cl ... Cl interactions. The unusual structural characteristics of 1 - 5 are attributed to the occurrence of intermolecular Te ... pi and pi...pi contacts associated with quinoid pi-electron delocalization across the para-dimethylaminophenyl ( 1 - 5) and para-ethoxyphenyl ( 5) groups.