Gold(i) complexes bearing mixed-donor ligands derived from N-heterocyclic carbenes

Abstract

The new 2-phenylthiocarbamoyl-1,3-dimesitylimidazolium inner salt (IMes·CSNPh) reacts with [AuCl(L)] in the presence of NH₄PF₆ to yield [(L)Au(SCNPh·IMes)]⁺ (L = PMe₃, PPh₃, PCy₃, CNBu^t). The carbene-containing precursor [(IDip)AuCl] reacts with IMes·CSNPh under the same conditions to afford the complex [(IDip)Au(SCNPh·IMes)]⁺ (IDip = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene). Treatment of the diphosphine complex [(dppm)(AuCl)₂] with one equivalent of IMes·CSNPh yields the digold metallacycle, [(dppm)Au₂(SCNPh·IMes)]²⁺, while reaction of [L₂(AuCl)₂] with two equivalents of IMes·CSNPh results in [(L₂){Au(SCNPh·IMes)}₂]²⁺ (L₂ = dppb, dppf, or dppa; dppb = 1,4-bis(diphenylphosphino)butane, dppf = 1,1′-bis(diphenylphosphino)ferrocene, dppa = 1,4-bis(diphenylphosphino)acetylene). The homoleptic complex [Au(SCNPh·IMes)₂]⁺ is formed on reaction of [AuCl(tht)] (tht = tetrahydrothiophene) with two equivalents of the imidazolium-2-phenylthiocarbamoyl ligand. This product reacts with AgOTf to yield the mixed metal compound [AuAg(SCNPh·IMes)₂]²⁺. Over time, the unusual trimetallic complex [Au(AgOTf)₂(SCNPh·IMes)₂]⁺ is formed. The sulfur-oxygen mixed-donor ligands IMes·COS and SIMes·COS (SIMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) were used to prepare [(L)Au(SOC·IMes)]⁺ and [(L)Au(SOC·SIMes)]⁺ from [(L)AuCl] (L = PPh₃, CN^tBu). The bimetallic examples [(dppf){Au(SOC·IMes)}₂]²⁺ and [(dppf){Au(SOC·SIMes)}₂]²⁺ were synthesized from the reaction of [(dppf)(AuCl)₂] with the appropriate ligand. Reaction of [(tht)AuCl] with one equivalent of IMes·COS or SIMes·COS yields [Au(SOC·IMes)₂]⁺ and [Au(SOC·SIMes)₂]⁺, respectively. The compounds [(Ph₃P)Au(SCNPh·IMes)]PF₆, [(Cy₃P)Au(SCNPh·IMes)]PF₆ and [Au(AgOTf)₂(SCNPh·IMes)₂]OTf were characterized crystallographically.