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
t
BuOK in the presence of AuCl(SMe
2
) 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.
Meet the new members of the golden family
: A new series of N‐heterocyclic carbene ligands bearing a rigid expanded‐ring backbone, supply unique stability to the gold(I) complex, and provide a high steric hindrance towards the metal center, which results in an excellent catalytic activity.