Kinetics of heterogeneous electron transfer on dicyanobis(tertiary phosphine) nickel complexes

Abstract

The potential step relaxation method has been employed to determine the heterogeneous standard rate constants k_s,h for the charge transfer reactions [Ni(CN)₂L₂]+e^–=[Ni(CN)₂L₂]^–(L = PPr₃; PEt₃; PEt₂Ph; PEtPh₂; ½dppe) in acetonitrile medium at a mercury electrode. It has been found that the k_s,h values increase slightly with the π-acceptor ability of the phosphine ligands for the complexes exhibiting a trans configuration, while a remarkable increase has been observed in passing from the trans complexes to cis-[Ni(CN)₂(dppe)].

Activation enthalpies and pre-exponential factors have been evaluated by measuring the k_s,h values in the range 0–40°C. The charge transfer mechanism and geometrical configuration of the reduced species are discussed.