Transition metal complexes of pyridine-N-oxides



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 [M(ONC5H5)6]^{2+} where M = Mn(II), Fe(II), Co(II), Ni(II). Many variations of pyridine N-oxide are known, such as the dioxides of 2,2'- and 4,4'-2,2'-bipyridine. Complexes derived from the trioxide of terpyridine have been crystallized as well.

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 C5H5NOH+, 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..