Collect. Czech. Chem. Commun. 2000, 65, 995-1013

Electrochemical Investigations of the Nickel(II)-Penicillamine System. 3. A Study of the Catalytic Hydrogen Prewave in Connection with Structure of Nickel(II)-Penicillamine Complexes

Florinel G. Banicaa,b,* and Ana Ionb

a Department of Chemistry, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
b Department of Analytical Chemistry and Instrumental Analysis, Polytehnica University of Bucharest, Calea Grivitei 132, 78 122 Bucharest, Romania


The catalytic hydrogen evolution on the dropping mercury electrode in the presence of Ni(II) and D-penicillamine (Pen) at pH around 6 yields a catalytic hydrogen prewave (CHP) with E1/2 = -1.21 V vs SCE. This wave is similar to the CHP produced by selenocysteine and cysteine described previously. The occurrence of the CHP depends on the formation of the mono(D-penicillamine-N,S)nickel(II) complex whereas bis(D-penicillamine-N,S)nickel(II) complex is inert and has no influence on the CHP electrode process. Although the analogous bis(cysteine) complex is labile, there is strong evidence that it does not take part directly in the CHP process in the Ni(II)-cysteine system. The actual proton donor in the CHP electrode process is the hydronium ion and not the acid component of the buffer. A tentative reaction mechanism was formulated with emphasis on the state of the intermediate hydrogen species. The characteristic pH, nickel ion involvement and the structure of the ligand make the CHP process an attractive model for hydrogen redox reactions catalyzed by [NiFe] hydrogenase.

Keywords: Electrocatalysis; Hydrogen evolution; Nickel complexes; Penicillamine; Polarography; Catalytic hydrogen prewave; Nickel hydrogenase; Amino acids.

References: 62 live references.