2 : 2 Fe(III): ligand and "adamantane core" 4 : 2 Fe(III): ligand (hydr)oxo complexes of an acyclic ditopic ligand

Morten Ghiladi, Frank B. Larsen, Christine J. McKenzie, Inger Søtofte, Jean-Pierre Tuchagues

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    A bis-hydroxo-bridged diiron(III) complex and a bis-mu-oxo-bis-mu-hydroxo-bridged tetrairon( III) complex are isolated from the reaction of 2,6-bis((N, N'-bis-(2-picolyl) amino) methyl)-4-tert-butylphenol (Hbpbp) with iron perchlorate in acidic and neutral solutions respectively. The X-ray structure of the dinuclear complex [{( Hbpbp) Fe(mu-OH)}(2)](ClO4)(4) center dot 2C(3)H(6)O ( 1 center dot 2C(3)H(6)O) shows that only one of the metal-binding cavities of each ligand is occupied by an iron( III) atom and two [Fe(Hbpbp)](3+) units are linked together by two hydroxo bridging groups to form a [ Fe(III) -(mu-OH)](2) rhomb structure with Fe center dot center dot center dot Fe = 3.109(1) angstrom. The non-coordinated tertiary amine of Hbpbp is protonated. Magnetic susceptibility measurements show a well-behaved weak antiferromagnetic coupling between the two Fe( III) atoms, J =- 8 cm(-1). The tetranuclear complex [(bpbp)(2)Fe-4(mu-O)(2)(mu-OH)(2)](ClO4)(4) (2) was isolated as two different solvates 2 center dot 4CH(3)OH and 2 center dot 6H(2)O with markedly different crystal morphologies at pH ca. 6. Complex 2 center dot 4CH(3)OH forms red cubic crystals and 2 center dot 6H(2)O forms green crystalline platelets. The Fe4O6 core of 2 shows an adamantane-like structure: The six bridging oxygen atoms are provided by the two phenolato groups of the two bpbp(-) ligands, two bridging oxo groups and two bridging hydroxo groups. The hydroxo and oxo ligands could be distinguished on the basis of Fe - O bond lengths of the two different octahedral iron sites: Fe -mu-OH, 1.953( 5), 2.013( 5) angstrom and Fe-mu-O, 1.803( 5), 1.802( 5) angstrom. The difference in ligand environment is too small for allowing Mossbauer spectroscopy to distinguish between the two crystallographically independent Fe sites. The best fit to the magnetic susceptibility of 2 center dot 4CH(3)OH was achieved by using three coupling constants J((Fe - OPh - Fe)) = 2.6 cm(-1), J((Fe - OH - Fe)) =- 0.9 cm(-1), J((Fe - O - Fe)) =- 101 cm(-1) and iron( III) single ion ZFS (| D| = 0.15 cm(-1)).
    Original languageEnglish
    JournalDalton Transactions (Print Edition)
    Issue number9
    Pages (from-to)1687-1692
    ISSN1477-9226
    Publication statusPublished - 2005

    Keywords

    • Structural characterization
    • Iron(III) Complexes
    • Coordination
    • Crystal-structures
    • Molecular-structure
    • Bridging ligands
    • Metal-complexes
    • Magnetic-properties
    • Cluster
    • Dinucleating ligand

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