Mechanism of the palladium-catalysed electrosynthesis of diethyl carbonate from carbon monoxide and ethanol

Abstract A mechanism is proposed for the PdBr2(PPh3)2-catalysed electrosynthesis of diethyl carbonate from carbon monoxide and ethanol, proceeding at room temperature and atmospheric CO pressure. The mechanism is investigated by cyclic voltammetry and 31P NMR spectroscopy. The active Pd0 complex able to coordinate CO is generated by the chemical reduction of PdBr2(PPh3)2 by EtO– ions generated from EtOH at the cathode. After reaction of EtO– ions with Pd0(PPh3)2(CO), the ensuing anionic complex [(PPh3)2Pd0–COOEt]– is oxidized at the anode in a key step leading to BrPdII–COOEt(PPh3)2. A nucleophilic attack of ethoxide on the latter generates diethyl carbonate and the Pd0 complex active in th…