Dramatic mechanistic switch in Sn/Au(I) group exchanges: transmetalation vs. oxidative addition

Area of Science:

• Organometallic chemistry
• Reaction mechanisms

Background:

• The phenyl/halide (Ph/X) exchange in organotin and gold complexes typically follows a concerted mechanism.
• This mechanism involves aryl/halide (Ar/X) mixed bridges.

Purpose of the Study:

• To investigate the mechanism of Ph/X exchange in reactions involving triphenylbutyltin (SnPh(n)Bu3) and gold(I) complexes ([AuXL]).
• To determine how the nature of the halide ligand (X) influences the reaction pathway.

Main Methods:

• Studied the reaction of SnPh(n)Bu3 with [AuXL] complexes where X = Cl or vinyl.
• Analyzed the reaction products and intermediates to elucidate the mechanism.

Main Results:

• When X = Cl, the Ph/X exchange proceeds via the usual concerted mechanism with Ar/X mixed bridges.
• When X = vinyl, the reaction unexpectedly switches to an oxidative addition/reductive elimination pathway.
• This pathway involves a transient gold(III) intermediate.

Conclusions:

• The mechanism of Ph/X exchange is highly dependent on the nature of the halide ligand.
• Vinyl ligands in [AuXL] complexes promote a novel Au(III)-mediated pathway for Ph/X exchange, distinct from the typical concerted route.