Syntheses, structures, and reactivity of low spin iron(III) complexes containing a single carboxamido nitrogen in a [FeN5L] chromophore

A new pentacoordinate ligand based on TPA (tris-(2-pyridylmethyl)amine), na mely, N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide (PaPy3 H), has been synthesized. The iron(III) complexes of this ligand, namely, [ Fe(PaPy3)(CH3CN)] (ClO4)(2) (1), [Fe(PaPy3)(Cl)]ClO4 (2), [Fe(PaPy3)(CN)]Cl O4 (3). and [Fe(PaPy3)(N3)]ClO4 (4), have been isolated and complexes 1-3 h ave been structurally characterized. These complexes are the first examples of monomeric iron(III) complexes with one carboxamido nitrogen in the firs t coordination sphere. All four complexes are low spin and exhibit rhombic EPR signals around g = 2. The solvent bound species [Fe(PaPy3)(CH3CN)](ClO4 )(2) reacts with H2O2 in acetonitrile at low temperature to afford [Fe(PaPy 3)(OOH)](+) (g = 2.24, 2.14, 1.96). When cyclohexene is allowed to react wi th H2O2 at room temperature, a significant amount oi cyclohexene oxide is p roduced along with the allylic oxidation products. Analysis of the oxidatio n products indicates that the allylic oxidation product, arise from a radic al-driven autoxidation process while the epoxidation is carried out by a di stinctly different oxidant. No epoxidation of cyclohexene is observed with 1/TBHP.