Oxidative Addition, Transmetalation, and Reductive Elimination at a 2,2′-Bipyridyl-Ligated Gold Center

Three-coordinate
bipyridyl complexes of gold, [(κ2-bipy)­Au­(η2-C2H4)]­[NTf2], are readily
accessed by direct reaction of 2,2′-bipyridine
(bipy), or its derivatives, with the homoleptic gold ethylene complex
[Au­(C2H4)3]­[NTf2]. The
cheap and readily available bipyridyl ligands facilitate oxidative
addition of aryl iodides to the Au­(I) center to give [(κ2-bipy)­Au­(Ar)­I]­[NTf2], which undergo first aryl-zinc
transmetalation and second C–C reductive elimination to produce
biaryl products. The products of each distinct step have been characterized.
Computational techniques are used to probe the mechanism of the oxidative
addition step, offering insight into both the origin of the reversibility
of this process and the observation that electron-rich aryl iodides
add faster than electron-poor substrates. Thus, for the first time,
all steps that are characteristic of a conventional intermolecular
Pd­(0)-catalyzed biaryl synthesis are demonstrated from a common monometallic
Au complex and in the absence of directing groups.