An Unusual Macrocyclic Hexamer of an Iso-Tellurazole N-Oxide Featuring CTe O Chalcogen Bonds is Formed by κ -O Complexation to Fe(II) and Ni(II).

Studies of the supramolecular chemistry of iso-tellurazole N-oxides have been confined to non-polar media until now. To overcome that limitation, an iso-tellurazole N-oxide was derivatized with a primary alcohol group; the compound is soluble in polar solvents and stable in acidic to neutral aqueous media. Nickel (II) and iron (II) form macrocyclic complexes with six molecules of that iso-tellurazole N-oxide in a hitherto not-observed macrocyclic arrangement defined by CTe⋅⋅⋅O chalcogen bonds and κ -O bound to the metal ion. This behaviour is in sharp contrast with the κ -Te (n=1,2,4) complexes formed by soft metal ions.