High spin d(5) complexes of tris(6-hydroxymethyl-2-pyridylmethyl)amine (H3L): hepta-coordinated [Mn(H3L)]Cl-2 and linear trinuclear [Fe3L2](ClO4)

Gregorio Guisado-Barrios, Yang Li, Alexandra M. Z. Slawin, David T. Richens, Ian A. Gass, Paul R. Murray, Lesley J. Yellowlees, Euan K. Brechin

Research output: Contribution to journalArticlepeer-review

Abstract

Reaction of MnCl2 center dot 4H(2)O with H3L (H3L = tris(6-hydroxymethyl-2-pyridylmethyl)amine) in methanol gives hepta-coordinated [Mn(H3L)]Cl-2 involving attachment of Mn(II) to all four nitrogens and three hydroxymethyl arms. Reaction of H3L with Fe(ClO4)(2)center dot 6H(2)O in CH3CN in the presence of NaO2CC6H5 in an attempt to make [(FeOH)-O-III(H3L)(O2CC6H5)](ClO4), a putative model for soybean lipoxygenase-1, instead gave rise to the linear triiron(III) complex [Fe3L2](ClO4)(3) with all three hydroxymethyl arms deprotonated and forming three alkoxide bridges between each Fe( III) centre. The central Fe(III) is hexa-coordinated to only the alkoxide bridges and flanked by two hepta-coordinated iron(III) centres analogous to the Mn(II) complex. [Fe3L2](ClO4)(3) exhibits two reversible 1e(-) reductions to mixed-valence [Fe3L2](2+) and [Fe3L2](+) forms. Structure data and magnetochemistry on [Fe3L2](ClO4)(3) reveals the tightest Fe-O-Fe angle (87.4 degrees) and shortest Fe center dot center dot center dot Fe distance (2.834 angstrom) yet found for any weakly antiferromagnetically-coupled high spin alkoxide-bridged di- or triiron(III) system and challenges current theories involved in correlating the extent/nature of magnetic interactions in such systems based on Fe-O(bridge) distances and Fe-O-Fe angles. The central hexa-alkoxide coordinated Fe(III) is novel and shows a remarkable resistance towards reduction to Fe(II).

Original languageEnglish
Pages (from-to)551-558
Number of pages8
JournalDalton Transactions
Issue number4
Early online date14 Nov 2007
DOIs
Publication statusPublished - 2008

Keywords

  • O-O BOND
  • NEUTRON-SCATTERING SPECTRA
  • BULK MAGNETIC-PROPERTIES
  • NONHEME IRON CATALYSTS
  • CRYSTAL-STRUCTURE
  • RIBONUCLEOTIDE REDUCTASE
  • SPECTROSCOPIC PROPERTIES
  • METHANE MONOOXYGENASE
  • ALKANE HYDROXYLATION
  • ELECTRONIC-STRUCTURE

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