Detection of Pd(III) and Pd(IV) Intermediates during the Aerobic Oxidative C–C Bond Formation from a Pd(II) Dimethyl Complex

The dimethyl PdII complex (MeN4)­PdIIMe2 (MeN4 = N,N′-dimethyl-2,11-diaza­[3,3]­(2,6)­pyridinophane) is
readily oxidized by dioxygen in the presence of protic solvents to
selectively eliminate ethane. UV–vis, EPR, ESI-MS, and NMR
studies reveal the formation of several PdIII and PdIV intermediates during the aerobically induced C–C
bond formation reaction, including the key intermediate [(κ3-MeN4)­PdIVMe3]+, which leads to ethane elimination. The latter complex was also
synthesized independently and structurally characterized to reveal
a distorted octahedral geometry that is proposed to promote facile
reductive elimination. Overall, this study represents a rare example
of aerobic oxidation of an organometallic PdII precursor
that leads to a well-defined PdIV species, which undergoes
selective C–C bond formation under ambient conditions.