Connecting Binuclear Pd(III) and Mononuclear Pd(IV) Chemistry by Pd–Pd Bond Cleavage

Oxidation of binuclear Pd­(II) complexes with PhICl2 or
PhI­(OAc)2 has previously been shown to afford binuclear
Pd­(III) complexes featuring a Pd–Pd bond. In contrast, oxidation
of binuclear Pd­(II) complexes with electrophilic trifluoromethylating
(“CF3+”) reagents has been reported
to afford mononuclear Pd­(IV) complexes. Herein, we report experimental
and computational studies of the oxidation of a binuclear Pd­(II) complex
with “CF3+” reagents. These studies
suggest that a mononuclear Pd­(IV) complex is generated by an oxidation–fragmentation
sequence proceeding via fragmentation of an initially formed, formally
binuclear Pd­(III), intermediate. The observation that binuclear Pd­(III)
and mononuclear Pd­(IV) complexes are accessible in the same reactions
offers an opportunity for understanding the role of nuclearity in
both oxidation and subsequent C–X bond-forming reactions.