Electrocatalytic radical degradation of 2-aminoethanol by nickel, palladium and platinum complexes bearing non-innocent diarylamido/bis(phosphine) pincer ligand

Abstract

The electrocatalytic activity of PNP pincer complexes with general formula (PNP)MCl (PNP is bis(2-diisopropylphosphino-4-methylphenyl)amide; M = nickel, palladium and platinum) in the oxidative 2-aminoethanol (MEA, a recalcitrant pollutant) degradation process was studied using cyclic voltammetry method. Complexes fulfil the requirements typically expected of a redox mediator or catalyst. Their electrochemical oxidation yields the aminyl radical species which unpaired electron is localized on the ligand. The mechanism of interaction of these aminyl radical complexes with MEA was studied using ESR- and NMR-spectroscopy methods. The addition of MEA to the solution of model platinum derivative leads to the disappearance of ESR signal responsible for the aminyl radical complex, whereas the ³¹P{¹H} NMR spectrum revealed the regeneration of neutral (PNP)MCl. Palladium derivative was found to be the most effective catalyst of the series with an I_cat/I_p value of 6.7. Controlled potential electrolysis has allowed us to identify the main products of the catalytic process and to propose the mechanism of the overall process.