Ligand-Induced Reductive Elimination of Ethane from Azopyridine Palladium Dimethyl Complexes

Reductive
elimination (RE) is a critical step in many catalytic processes.
The reductive elimination of unsaturated groups (aryl, vinyl and ethynyl)
from Pd­(II) species is considerably faster than RE of saturated alkyl
groups. Pd­(II) dimethyl complexes ligated by chelating diimine ligands
are stable toward RE unless subjected to a thermal or redox stimulus.
Herein, we report the spontaneous RE of ethane from (azpy)­PdMe2 complexes and the unique role of the redox-active azopyridine
(azpy) ligands in facilitating this reaction. The (azpy)­PdMe2 complexes are air- and moisture-stable in the solid form, but they
readily produce ethane upon dissolution in polar solvents at temperatures
from 10 °C to room temperature without the need for an external
oxidant or elevated temperatures. Experimental and computational studies
indicate that a bimolecular methyl transfer precedes the reductive
elimination step, where both steps are facilitated by the redox-active
azopyridine ligand.