Low-spin iron(II) in a small unsymmetrical N6 macrocycle

Abstract

A small unsymmetrical N₆ macrocycle has been prepared by template methods, from 2,6-di[N-(3-aminopropyl)aminomethyl]pyridine I and 2,6-diacetylpyridine, as [BaL¹][ClO₄]₂ 1. Transmetallation with iron(II) perchlorate, in air, yielded an intense dark purple complex, [FeL¹][ClO₄]₂ 2. A single-crystal structure determination of 2 revealed that the iron(II) ion has a distorted N₆ octahedral geometry. Wrapping of this small, fairly inflexible macrocycle around the octahedral sites on the iron atom is facilitated by the presence of the two amine bonds. The iron(II) is low spin and the ¹H and ¹³C NMR spectra are correspondingly sharp and unshifted.