Gold complexes of ditelluridoimidodiphosphinate ligands — Reversible oxidation of Au(I) to Au(III) via insertion of gold into a phosphorus–tellurium bond
The reaction of (THT)AuCl with (TMEDA)Na[N(TePR2)2] (R = Ph, i-Pr, t-Bu) produces a series of gold (III) complexes of the type [{R2PNP(Te)R2}Au(µ-Te)]2 (4a, R = i-Pr; 4b, R = Ph; 4c, R = t-Bu) rather than the expected homoleptic Au(I) complexes of the ditelluridoimidodiphosphinate ligands. A combination of solution- and solid-state NMR studies shows that both cis and trans isomers of 4a–4c are formed in these reactions. X-ray structural determinations of the trans isomers of 4a–4c reveal a centrosymmetric arrangement with a central four-membered Au2Te2 ring formed by the formal insertion of gold into a P–Te bond; this insertion process was shown to be reversible upon addition of PPh3 to 4a to give the monomeric gold(I) complex Ph3PAu[N{TeP(i-Pr)2}2]. The X-ray structure of cis-4b is also described.Key words: gold, tellurium, redox, X-ray structures, imidodiphosphinate.