Stereospecific chlorotelluration of terminal acetylenes

► Terminal acetylenes insert into TeIV-Cl bond to give vinyltellurium(IV) dichlorides. ► The vinyl group adopts Z-conformation irrespective of the bulky aryl group at Te. ► Retention of conformation on exchange or removal of the halo ligands. ► Intramolecular Te⋯Cl interaction favors the Z conformation of the vinyl group. ► Steric bulk of the aryl ligands affects the self assembly via Te⋯Cl interactions.