Low temperature reaction of [Fe(TPA)(CH3CN)2]~(2+0 with excess 3-chloroperoxybenzoic acid in semi-frozen acetonitrile; EPR detection of an acylperoxo iron(III) adduct

摘要

Treatment of i(TPA)Fe~(II)(CH3CN)2]~(2+) (TPA = tris(2-pyridylmethyl)amine) with excess (>2 Eq) of 3-chloroperoxybenzoic acid (mCPBA) in semi-frozen acetonitrile in liquid N2 vapour generates a rhombic EPR signal assigned to the S = 1/2 low spin acylperoxoiron(IIl) species [(TPA)Fe(O3CC6H4-3Cl)(CH3CN)]~(2+) 5; the elusive precursor on the pathway to [(TPA)Fe~(III)(5-chlorosalicylate)]~+ 4 via putative [(TPA) Fe~(II)(O)(O2CC6H4-3Cl)]~(2+). Formation of cyclohexene epoxide in the presence of added cyclohexene at low temperatures (<—40 °C) suggests that intermolecular alkene epoxidation competes successfully with the intramolecular reactions involving 5 to generate 4.