Electrochemical Studies of Transition Metal Carbonyls

Author

Dwayne Edward Cooper, Eastern Illinois University

Degree Name

Master of Science (MS)

Semester of Degree Completion

1986

Thesis Director

Edward O. Sherman

Thesis Committee Member

Richard L. Keiter

Abstract

The electrochemical oxidation of (OC)₅MP-PM'(CO)₅ (M=Cr, Mo, W; M'=Cr, Mo, W; M=M' or M≠M'; P-P=Ph₂PCH₂CH₂PPh₂) and the reduction of the oxidized products in a 0.1 M tetrabutyl-ammonium perchlorate methylene chloride solution at a platinum disc working electrode with a Ag/AgCl reference electrode have been studied. The number of electrons in the oxidation step was determined by comparison with the one electron oxidation of ferrocene which had a peak potential at +0.15 V.

The cyclic voltammograms of the homobimetallic and heterobimetallic complexes display two general chacteristics: quasi-reversible or irreversible one electron oxidation of each individual metal center. The chromium-chromium complex exhibits two oxidation peaks with peak potentials at +1.04 V and +1.35 V. The first oxidation peak coupled with a cathodic peak exhibits quasi-reversible behavior while the second oxidation peak exhibits irreversible behavior. The molybdenum and tungsten homobimetallic species each possess an irreversible oxidation peak at 1.06 V and 1.12 V, respectively. The heterobimetallics all exhibit irreversible behavior. The voltammograms have a single oxidation peak without a coupled cathodic peak. The anodic peak potentials occur at +0.94, +0.96, and +1.05 volts for the chromium-molybdeum, chromium-tungsten, and molybdenum-tungsten complex, respectively.

Cyclic voltammograms were also obtained for (OC)₄W(Ph₂P)₂W(CO)₄ (III) and HPh₂P(OC)₃W(Ph₂P)₂W(CO)₃PPh₂H (IV). The first oxidation step was coupled to a cathodic peak for each of the phosphido-bridged complexes. The peak to peak separations and peak ratios exhibit reversible behavior. The anodic peak potential for (III), corresponding to a two electron change, occurs at +0.75 V.

For complex (IV) the anodic peak potential, corresponding to a one electron change, was found at +0.19 V.

Complexes (III) and (IV) undergo second oxidation steps which are irreversible as shown by the absence of a cathodic peak. For complex (III), the second anodic peak potential was found at +1.02 V with a peak height equal to two electrons.

Complex (IV) loses a second electron at +0.72 V and a third electron at +1.4 V, accompanied by formation of metal-metal bonds of bond order 2 and 2 1/2, respectively.

Recommended Citation

Cooper, Dwayne Edward, "Electrochemical Studies of Transition Metal Carbonyls" (1986). Masters Theses. 2637.
https://thekeep.eiu.edu/theses/2637