THE COORDINATION CHEMISTRY OF MIXED PYRIDINE-PHENOL LIGANDS - SYNTHESES AND CRYSTAL-STRUCTURES OF MN(III) AND NI(II) COMPLEXES OF 2-(2-HYDROXYPHENYL) PYRIDINE

The complexes [Mn(L(1))(3)] (1) and [Ni-2(L(1))(2)(dmf)(6)] [BPh(4)](2) (2) have been 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-N3O3 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 CH2Cl2. Complex 2 in contrast is binuclear, with two Ni(II) centres and two ligands L' each of which donates its pyridyl residue to one metal and shares its phenolate group between both metals, affording a Ni-2(mu-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.