Two-electron oxidation of N,N,N′,N′-tetramethylphenylenediamine with a chromium(v) salen complex

Abstract

The oxidation of tetramethylphenylenediamine (TMPD) with (salen)CrVO+ generates initially the 2-electron product TMPD2+, followed by the reaction with excess TMPD to yield the radical cation, TMPD+. The kinetics of both TMPD/(salen)CrVO+ and TMPD/TMPD2+ reactions are acid-dependent, with TMPD being the most reactive form, and the doubly protonated TMPDH2(2+) exhibiting no discernible reactivity toward either (salen)CrVO+ or TMPD2+. The specific rate constants for the individual reactions are: TMPD/(salen)CrVO+, k=(6.28+/-0.50)x10(9) M(-1) s(-1), TMPDH+/(salen)CrVO+, (3.89+/-0.31)x10(5), TMPD/TMPD2+, (7.61+/-0.42)x10(8), and TMPDH+/TMPD2+, (3.46+/-0.22)x10(4).