Probing the Formation of the NHC-Palladium Species in Ionic Liquids by X-ray Photoelectron Spectroscopy

We investigate the formation of the N-heterocyclic carbene palladium species in 1-butyl-3-methylimidazolium acetate, using X-ray photoelectron spectroscopy. The formation of the carbene species leads to a more negatively charged palladium atom, which shows lower binding energy. Meanwhile, a second electronic environment is observed for the N 1 s spectrum showing lower binding energy. It suggests that the bonding of the imidazolium cation and the palladium atom causes the change of the distribution of the positive charge on the nitrogen atom, which is reflected on the N 1 s binding energy.