Valence tautomerism in octahedral and square-planar phenoxyl-nickel(II) complexes: are imino nitrogen atoms good friends?.

The two tetradentate salen-type ligands I (H2L) and II [R = Me (H2LMe)] afford the slightly distorted square-planar low-spin NiII complexes [Ni(L)] (1) and [Ni(LMe)] (2), which comprise two coordinated phenolate groups. Complex 1 was electrochem. oxidized into 1+, which contains a coordinated phenoxyl radical, with a contribution from the Ni orbital. In the presence of pyridine, 1+ is converted into 1Py+, an octahedral phenolate Ni(III) complex with two pyridines axially coordinated; an intramol. electron transfer (valence tautomerism) is promoted by the geometrical changes, from square planar to octahedral, around the metal center. The tetradentate ligand H2LMe, in the presence of pyridine, and the hexadentate ligand II [R = 2-pyridylmethyl (H2LPy)] in CH2Cl2 afford, resp., the octahedral high-spin NiII complexes 2Py and [Ni(LPy)] (3), which involve two equatorial phenolates and two axially coordinated pyridines. At 100 K, the 1-electron-oxidized product 2Py+ comprises a phenoxyl radical ferromagnetically coupled to the high-spin NiII ion, with large zero-field splitting parameters, while 3+ involves a phenoxyl radical antiferromagnetically coupled to the high-spin NiII ion. [on SciFinder(R)]

Références

Titre
Valence tautomerism in octahedral and square-planar phenoxyl-nickel(II) complexes: are imino nitrogen atoms good friends?.
Type de publication
Article de revue
Année de publication
2006
Revue
Chem. - A Eur. J.
Volume
12
Pagination
6953–6962
ISSN
0947-6539
Soumis le 12 avril 2018