Electrochemical Studies of Iron, Cobalt, and Nickel Complexes of Bidentate Phosphine Thioether Ligands

Author

Robert L. Turner, Eastern Illinois University

Degree Name

Master of Science (MS)

Semester of Degree Completion

1987

Thesis Director

Richard L. Keiter

Abstract

The electrochemical behavior of a series of cationic complexes, [Ni(S-P)₂]²⁺, [Fe(S-P)₂(CH₃CN)_2.5]²⁺ and [Co(S-P)₂CH₃CN]²⁺, where S-P= (C₆H₅)₂PCH₂CH₂SCH₂CH₃, has been examined in acetonitrile on mercury and platinum electrodes. The nickel compound was reduced in two reversible diffusion controlled, one-electron transfers. Addition of PPh₃ (Ph=C₆H₅) and S-P caused a positive potential shift in the nickel(I) to nickel(0) wave. An EC mechanism was postulated to account for this shift. The chemical reaction was believed to be substitution of the phosphine substrate with opening of the chelate ring. The cobalt compound was reduced in three diffusion controlled, one-electron transfers, and oxidized in a quasi-reversible, diffusion controlled one-electron transfer. The cobalt(II) to cobalt(I) and the cobalt(0) to cobalt(-1) waves were reversible while the cobalt(I) to cobalt(0) was quasi-reversible. The quasi-reversible behavior suggested an EC mechanism with the loss of acetonitrile. Addition of PPh₃ and S-P caused a positive potential shift in the cobalt(I) to cobalt(O) wave. The same type of substitution reaction observed for nickel was believed responsible for the potential shift. The iron compound was reduced in two one-electron transfers which were kinetically controlled, and oxidized in a single one-electron transfer which was diffusion controlled. The oxidation was quasi-reversible while both reductions were irreversible.

Recommended Citation

Turner, Robert L., "Electrochemical Studies of Iron, Cobalt, and Nickel Complexes of Bidentate Phosphine Thioether Ligands" (1987). Masters Theses. 2603.
https://thekeep.eiu.edu/theses/2603