Influence of electrolyte concentration on coupled chemical reactions Part 1Reduction of CoII(salen)in aprotic solvents
Abstract
The reduction of CoII(salen) has been investigated using Au microdisc electrodes in DMF containing several electrolytes, concentrations in the range 0.1–100 mM. The kinetics of the CoII(salen)/CoI(salen)- couple are always rapid but the formal potential of the couple depends on the cation of the electrolyte and its concentration. The data may be interpreted in terms of ion pairing between CoI(salen)- and the cation of the electrolyte, increasing along the series Bu4N+<Na+<Li+. In contrast, the formal potential for the CoIII(salen)+/CoII(salen) couple is insensitive to the choice of the electrolyte and its concentration. It is also demonstrated that the rate constant for the reaction of CoI(salen)- with BuBr decreases with increased electrolyte concentration and this is interpreted in terms of a decreased nucleophilicity, again due to ion pairing.