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) Å, 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.