Transition metal nitroso complexes

[1] Organic nitroso compounds bind to metals in several ways, but most commonly as monodentate N-bonded ligands.

Dimers of organic nitroso compounds also bind in a κ2--O,O bidentate manner.

More complicated but more biorelevant routes involve degradation of precursors such as nitrobenzene and phenylhydroxylamine.

[1] Methemoglobinemia is a disorder where a large fraction of hemoglobin in one's blood has converted to inactive forms, generically called methemoglobin.

[6] As indicated by the applications in dyeing, chelating aryl nitroso compounds often form deeply colored complexes

Structure of the dye Naphthol Green B , which features of nitroso ligand bound to Fe(III).
Trapping of 1,2-dinitrosobenzene by Ru(II)
Structure of Fe( octaethylporphyrin )(C 6 H 5 NO)(imidazole). This synthetic complex is thought to resemble heme inhibited by nitroso benzene. Color code: red = O, blue = N, Fe, gray = C, white = H.