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

Abstract

The oxidation of tetramethylphenylenediamine (TMPD) with (salen)Cr^VO⁺ 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)Cr^VO⁺ and TMPD/TMPD²⁺ reactions are acid-dependent, with TMPD being the most reactive form, and the doubly protonated TMPDH₂²⁺ exhibiting no discernible reactivity toward either (salen)Cr^VO⁺ or TMPD²⁺. The specific rate constants for the individual reactions are: TMPD/(salen)Cr^VO⁺, k = (6.28 ± 0.50) × 10⁹ M⁻¹ s⁻¹, TMPDH⁺/(salen)Cr^VO⁺, (3.89 ± 0.31) × 10⁵, TMPD/TMPD²⁺, (7.61 ± 0.42) × 10⁸, and TMPDH⁺/TMPD²⁺, (3.46 ± 0.22) × 10⁴.