Transition metal complexes of pyridine-N-oxides explained

Transition metal complexes of pyridine-N-oxides encompass coordination complexes that contain pyridine-N-oxides as ligands. Particularly common are the octahedral homoleptic complexes of the type where M = Mn(II), Fe(II), Co(II), Ni(II).^[1] Many variations of pyridine N-oxide are known, such as the dioxides of 2,2'- and 4,4'-2,2'-bipyridine.^[2] Complexes derived from the trioxide of terpyridine have been crystallized as well.^[3]

Structure and bonding

Pyridine-N-oxides bind to metals through the oxygen. According to X-ray crystallography, the M-O-N angle is approximately 130° in many of these complexes. As reflected by the pKa of 0.79 for, pyridine N-oxides are weakly basic ligands. Their complexes are generally high spin, hence they are kinetically labile.

Applications

Zinc pyrithione is a coordination complex of a sulfur-substituted pyridine-N-oxide. This zinc complex has useful fungistatic and bacteriostatic properties..^[4]

References

1. 10.1021/cr00074a001. Structural and Magnetic Properties of Transition Metal complexes of Pyridine N-Oxide . 1986 . Carlin . Richard L. . De Jongh . L. J. . Chemical Reviews . 86 . 4 . 659–680 . free .
2. Book: 10.1007/430_2008_9. Supramolecular Chemistry of 4,4′-Bipyridine-N,N′-dioxide in Transition Metal Complexes: A Rich Diversity of Co-ordinate, Hydrogen-Bond and Aromatic Stacking Interactions . Molecular Networks . Structure and Bonding . 2009 . Jia . Junhua . Hubberstey . Peter . Champness . Neil R. . Schröder . Martin . 132 . 135–161 . 978-3-642-01366-9 .
3. 10.1039/b008993l . Geometrical preferences of complexes of terpyridine N-oxide ligands: Synthesis and crystal structures of nickel(II) with terpyridine 1,1′,1″-trioxide, terpyridine 1,1″-dioxide and terpyridine 1-oxide . 2001 . Amoroso . Angelo J. . Burrows . Miles W. . Dickinson . Anthony A. . Jones . Cameron . Willock . David J. . Wong . Wing-Tak . Journal of the Chemical Society, Dalton Transactions . 3 . 225–227 .
4. Structural characterization of bis(N-oxopyridine-2-thionato)zinc(II) . . 1977 . 16 . 8 . 1834–8 . 10.1021/ic50174a002 . Barnett, B. L. . Kretschmar, H. C. . Hartman, F. A. .