Electrochemistry of Bismuth in a 67 Mole% AlCl3 ‐ 33 Mole% N‐(n‐Butyl)Pyridinium Chloride Room Temperature Molten Salt

The electrochemical reduction of Bi 3+ ion in a 2:1 AlCl 3 ‐ N ‐ ( n ‐ butyl ) pyridinium chloride melt at glassy carbon electrodes results in the formation of Bi 5 3 + ion. The further reduction of this cluster ion to the metal is the sum of two processes: ( i ) the reversible two‐electron reduction of the closo‐trigonal bipyramid with the formation of a closed shell nido‐square pyramid and ( ii ) the reduction of this unstable intermediate to the metal. On glassy carbon electrodes both processes give rise to separate waves because the deposition of the metal is retarded by nucleation phenomena. Anodization of the metal, or reaction of the metal with BiCl 3 , produces Bi 5 3 + ion [or its solid salt Bi 5 ( AlCl 4 ) 3 ] and minor traces of another low‐valent species, probably “ BiAlCl 4 . ” The anodic oxidation of Bi 5 3 + ion to Bi 3+ ion is irreversible but the mechanism of the reaction is not well understood.