Telluranes: potential synthons for charge-transfer complexes (involving hypervalent Te–I bonds) and serendipitous synthesis of the first triphenyl methyl phosphonium salts containing [C4H8TeI4]2− and [TeI6]2−anions

Hypervalent Te–I bonds of telluranes (C4H8TeI2, C5H10TeI2 and α-Me2TeI2) have been utilised to form the charge transfer (CT) complexes (1–3). The reaction of cyclic tellurane (1,1-diiodotetrahydro tellurophene, C4H8TeI2) with I2/ICl yields C8H16Te2I6 [IC4H8TeI–I–I–ITeC4H8I] (1); an unusual dinuclear species while the reaction of another cyclic tellurane (1,1-diiodo telluracyclohexane, C5H10TeI2) with I2 yields C5H10TeI4 (2) possessing different structural motif than 1. In 2 the iodine molecules are on both sides bonded to iodine atom of hypervalent Te–I bond of C5H10TeI2 which is analogous to the structural type present in Me2TeI4 (3) obtained by the reaction of α-Me2TeI2 with ICl. The reaction of C4H8TeI2 with PPh3, serendipitously, yields the first triphenyl methyl phosphonium salts [PPh3Me]2 2+[C4H8TeI4]2− (4) and [PPh3Me]2 2+[TeI6]2− (5), indicating the oxidation of PPh3 whereas C4H8TeI2 itself, is converted into [C4H8TeI4]2− and [TeI6]2− anions. All the complexes 1–5 have been characterised through single crystal X-ray diffraction studies.