Kinetic Data on the Synergetic Role of Amines and Water in the Reduction of Phosphine‐Ligated Palladium(II) to Palladium(0)

Tertiary amines such as EtN( i Pr) 2 do not reduce [PdCl 2 (PPh 3 ) 2 ] into a Pd 0 complex. The latter is formed only after the addition of water (generation of HO – ), as was reported by Grushin and Alper for NEt 3 . The mechanism of the Pd II /Pd 0 reduction performed in the presence of an excess amount of PPh 3 is established quantitatively by means of electrochemical techniques that provide kinetic data (determination of the equilibrium and rate constants) for the disappearance of [PdCl 2 (PPh 3 ) 2 ] and the formation of [Pd 0 (PPh 3 ) 3 ]. [PdCl(OH)(PPh 3 ) 2 ] is formed, which allows reductive elimination between OH and the ligated PPh 3 (zero‐order reaction for PPh 3 ), and this leads to a Pd 0 complex. The reducing agent is ligated PPh 3 , which ultimately yields (O)PPh 3 . The rate of the overall reduction process is controlled by the amount of water that imposes the concentration of HO – .