Gold(I) Complexes Stabilized by Nine- and Ten-Membered N-Heterocyclic Carbene Ligands.

Abstract

Nine‐ and ten‐membered N‐heterocyclic carbene (NHC) ligands have been developed and for the first time their gold(I) complexes were synthesized. The protonated NHC pro‐ligands 2 a–h were prepared by the reaction of readily available N,N′‐diarylformamidines with bis‐electrophilic building blocks, followed by anion exchange. In situ deprotonation of the tetrafluoroborates 2 a–h with tBuOK in the presence of AuCl(SMe2) provided fast access to NHC‐gold(I) complexes 3–10. These new NHC‐gold(I) complexes show very good catalytic activity in a cycloisomerization reaction (0.1 mol % catalyst loading, up to 100 % conversion) and their solid‐state structures reveal high steric hindrance around the metal atom (%V bur up to 53.0) which is caused by their expanded‐ring architecture.