Metal Ion-Coupled Electron Transfer of a Nonheme Oxoiron(IV) Complex: Remarkable Enhancement of Electron-Transfer Rates by Sc3+

Rates of electron transfer from a series of one-electron reductants to a nonheme oxoiron(IV) complex, [(N4Py)Fe(IV)(O)](2+), are enhanced as much as 10(8)-fold by addition of metal ions such as Sc(3+), Zn(2+), Mg(2+), and Ca(2+); the metal ion effect follows the Lewis acidity of metal ions. The one-electron reduction potential of [(N4Py)Fe(IV)(O)](2+) is shifted to a positive direction by 0.84 V in the presence of Sc(3+) ion (0.20 M).