The
microscopic reverse of the transmetalation step in the Pd/M (M = Cu,
Ag, Au) catalyzed Sonogashira-type reactions has been observed in
the gas phase upon collision-induced dissociation (CID) of the heterobimetallic
complexes. Measuring the activation energies by quantitative energy-resolved
CID experiments provides an upper bound for the internal rearrangement
energies. The potential-energy surface is investigated by density
functional theory calculations and compared to the experimental values