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

The dimethyl Pd II  complex ( Me N4)Pd II Me 2  ( Me N4 =  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 Pd III  and Pd IV  intermediates during the aerobically induced C–C bond formation reaction, including the key intermediate [(κ 3 - Me N4)Pd IV Me 3 ] + , 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 Pd II  precursor that leads to a well-defined Pd IV  species, which undergoes selective C–C bond formation under ambient conditions.