Telluroether to Telluroxide Conversion in the Coordination Sphere of a Metal: Oxidation-Induced Umpolung of a Te–Au Bond

While Ph2Te is oxidized into Ph2TeCl2 in the presence of (tht)AuCl (tht = tetrahydrothiophene), reaction of (o-(Ph2P)C6H4)2Te (LTeP2) with the same gold reagent affords the complex LTeP2AuCl (1). Upon reaction with Ph3P, this complex is converted into [LTeP2AuPPh3][Cl] ([2][Cl]). Complex 1 also reacts with H2O2 to afford the telluroxide gold chloride complex (o-(Ph2P)C6H4)2Te(═O)AuCl (3). The three new complexes have been fully characterized. Their crystal structures indicate the presence of a Te–Au bond with lengths of 2.874(4), 2.937(2), and 2.9864(5) A, for 1, [2][Cl], and 3, respectively. Natural bond orbital analysis shows that oxidation of 1 into 3 results in an umpolung of the Te–Au bond which switches from Te→Au in 1 to Te←Au in 3. These results show that the telluroxide moiety of 3 acts as a Z-type ligand.