Hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine

Non-heme iron halogenases, such as SyrB2 and CytC3, catalyze the regioselective chlorination and bromination of aliphatic C–H bonds. Reported here is the hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen). The reactions between these coordination compounds and meta-chloroperbenzoic acid generate oxidants capable of oxidizing weak C–H bonds to C–Cl bonds. This chemistry is regioselective, with a strong preference for activating C–H bonds on secondary carbons over weaker C–H bonds on tertiary carbons. The reactivity is consistent with the methyl groups on the ligands preventing more sterically encumbered substrates from accessing the reactive portions of a [MIV(LMen)(O)Cl2] oxidant. The iron compounds promote more hydrocarbon chlorination than their manganese analogs.

Figure optionsDownload high-quality image (130 K)Download as PowerPoint slideResearch highlights▶ Metal complexes with bispicen derivatives chlorinate benzylic substrates. ▶ [MIV(L)(O)Cl2] species are believed to be responsible for the chlorination. ▶ Iron leads to superior chlorination activity than manganese. ▶ Increased ligand methylation leads to regioselectivity.