The coordination chemistry of mixed pyridine-phenol ligands; syntheses and crystal structures of Mn(III) and Ni(II) complexes of 2-(2-hydroxyphenyl)pyridine

Abstract

The complexes [Mn(L) 1) 3] ( 1) and [Ni 2(L 1 2(dmf) 6] [BPh 4] 2 ( 2) have prepared and crystallographically characterised (L 1 is the N,O-bidentate chelating anion of 2-(2-hydroxyphenyl) pyridine. Complex 1 comprises neutral tris-chelate Mn(III) units, with a mer-N 3O 3 donor set, which display Jahn-Teller distortion characteristic of the high-spin d 4 configuration. It is typical of other M III(L 1) 3 complexes that have recently been characterised, and undergoes a reversible Mn(III)/Mn(IV) couple at +0.03 V versus Fc/Fc + in CH 2Cl 2. Complex 2 in contrast is binuclear, with two Ni(II) centres and two ligands L 1 each of which donates its pyridyl residue to one metal and shares its phenolate group between both metals, affording a Ni 2 (μ-O) 2 core. The remaining three sites on each octahedral Ni(II) centre are occupied by O-bound dmf ligands from the recrystallisation solvent. This is the first example of L 1 acting as a bridging ligand via the phenolate oxygen atoms.