Transition metal nitroso complexes are coordination complexes containing one or more organonitroso ligands (RNO).[1]
thumb|right|Structure of the dye Naphthol Green B, which features of nitroso ligand bound to Fe(III).Organic nitroso compounds bind to metals in several ways, but most commonly as monodentate N-bonded ligands. Also known are O-bonded, η2-N,O-bonded. Dimers of organic nitroso compounds also bind in a κ2--O,O bidentate manner.
Organic nitroso complexes can be prepared from preformed organic nitroso precursors. These precursors usually exist as N-N bonded dimers, but the dimer dissociates readily. This direct method is used to give W(CO)5(tert-BuNO) (where tert-Bu is).[2] The Fe-porphyrin complex depicted below is prepared by this route. More complicated but more biorelevant routes involve degradation of precursors such as nitrobenzene and phenylhydroxylamine.[3]
(Et = C2H5, i-Pr = (CH3)2CH)
The coupling of organic ligands and nitric oxide is yet another route.[1]
Methemoglobinemia is a disorder where a large fraction of hemoglobin in one's blood has converted to inactive forms, generically called methemoglobin. Since methemoglobin is not an oxygen-carrier, methemoglobinemia is a serious disorder, sometimes fatal. Exposure to nitrobenzene, aniline, and their derivatives cause this disorder, which is attributed to their conversion to nitrosobenzene (and derivatives), which inactivate hemoglobin by forming a complex with the Fe center, precluding binding of O2.[4]