“…Among the molecular structures of unsymmetrical diorganotellurium(IV) dihalides 2a, 2b and 3a, the carbonyl O atom of the sole functionalized ligand is involved simultaneously in the intramolecular secondary bonding interaction to either of its heavier congeners. The observed internuclear distance between O and Te atoms, which is shorter than the sum of their van der [16]. The functionalized ligand thus prefers (C, O), rather than (C, S), mode of chelation, though the latter, involving its trans conformation, would have resulted in the formation of a less strained fivemember intramolecular ring.…”