Synthesis, X-ray characterisation and spectroscopic studies of metal complexes of N,N′-1,2-xylene-α,α′-diylbis(pyridin-2-one)

Abstract

The co-ordination modes adopted by N,N′-1,2-xylene-α,α′-diylbis(pyridin-2-one)(o-xbp) with Sc, Y, lanthanides, Th^IV, Mn^II, Fe^III, Co^II and Zn^II have been studied. Five representative complexes have been structurally characterised by single-crystal X-ray diffraction. In the monomeric ten-co-ordinate complex [Ce(o-xbp)₂(NO₃)₃]·MeOH both o-xbp ligands form eleven-membered chelate rings. In the dinuclear complex [Y₂(o-xbp)₃(NO₃)₆]·3MeCN pairs of nine-co-ordinate Y atoms are linked by an o-xbp bridge, whilst the other o-xbp ligands form chelate rings. The dinuclear complex [{Zn(o-xbp)Cl₂}₂] forms individual 22-membered rings in which pairs of tetrahedrally co-ordinated Zn atoms are linked by o-xbp bridges. In the iron(III) complex [Fe(o-xbp)₂Cl₂][FeCl₄]·MeOH the Fe atom in the cation has cis-octahedral co-ordination geometry with the o-xbp ligands forming eleven-membered chelate rings; the anion is tetrahedral. In the cobalt(II) complex [Co(o-xbp)₂(MeOH)₂]I₂·2MeOH the o-xbp ligands also chelate but the Co atom has a trans-octahedral geometry in which the two axial ligands are methanol molecules. A distinctive pattern of ligand conformations is observed in this series of compounds. Relevant spectroscopic results are also given.