Mechanism of Reduction of 2,2-Dibromomethyl-1,3-propanediol by Ni I-Tetraazamacrocyclic Complexes in Aqueous Solution - A Pulse Radiolysis and Electrochemical Study

Abstract

The reduction, catalytic reduction and the electrocatalytic reduction of halo-organic compounds are of major interest due to their role as pollutants. The mechanism and kinetics of reduction of 2,2-dibromomethyl-1,3-propanediol by several NiI tetraazamacrocyclic complexes, (NiIL i)+ (i = 1-4), in aqueous solutions to yield Br - and the non-halogenated compound was studied using the pulse radiolysis technique. The rate constants k = 5.3 × 108, 1.6 × 107, 6.0 × 105 and 3.5 × 10 4 M-1S-1 for L1, L2, L3 and L4 respectively, of the reactions (Ni ILi)+ RBr → (NiIIL i)2+ + Br- + R. increase with the free-energy gain in the reaction. All these complexes are good electrocatalysts for the reduction of this substrate. The mechanisms of the reductions is are discussed. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.