Kinetics of Disproportionation of Tricarbonylbis(phosphine)iron(I) Cation Radicals Probed by Double Potential Step Chronocoulometry

Rates of substitution of carbon monoxide in a series of iron(I) radical complexes were measured by using double potential step chronocoulometry, a transient electrochemical technique. Carbon monoxide substitution in Fe(CO)3L2+ (L = a phosphine) radicals proceeds solely by a second-order process that is first order in both the metal radical and the entering pyridine nucleophile. The rate of substitution depends on the basicity and size of the Lewis base, as seen in the L = PPh3 system, where kxvaries over 400-fold from 0.27 to 1.01 X 102 M“l s’1. Hammett analysis of the rate data shows that log k1 correlates well with the

Duke Scholars

Author Michael J. Therien Chemistry