Abstract Mechanism of substrate oxidations with hydrogen peroxide in the presence of a highly reactive, biomimetic, iron aminopyridine complex,[Fe II (bpmen)(CH 3 CN) 2][ClO 4] 2 (1; bpmen= N, N'-dimethyl-N, N'-bis (2-pyridylmethyl) ethane-1, 2-diamine), is elucidated. Complex 1 has been shown to be an excellent catalyst for epoxidation and functional-group- directed aromatic hydroxylation using H 2 O 2, although its mechanism of action remains ...