Dicoordinate Au(I)–Ethylene Complexes as Hydroamination Catalysts

A series of gold­(I)–ethylene
π-complexes containing a family of bulky phosphine ligands
has been prepared. The use of these sterically congested ligands is
crucial to stabilize the gold­(I)–ethylene bond and prevent
decomposition, boosting up their catalytic performance in the highly
underexplored hydroamination of ethylene. The precatalysts bearing
the most sterically demanding phosphines showed the best results reaching
full conversion to the hydroaminated products under notably mild conditions
(1 bar of ethylene pressure at 60 °C). Kinetic analysis together
with density functional theory calculations revealed that the assistance
of a second molecule of the nucleophile as a proton shuttle is preferred
even when using an extremely congested cavity-shaped Au­(I) complex.
In addition, we have measured a strong primary kinetic isotopic effect
that is consistent with the involvement of X–H bond-breaking
events in the protodeauration turnover-limiting step.