Cupferron is jargon for the ammonium salt of the conjugate base derived from N-nitroso-N-phenylhydroxylamine. This conjugate base is abbreviated as CU<sup>âÂÂ</sup>. It once was a common reagent for the complexation of metal ions, being of interest in the area of qualitative inorganic analysis. Its formula is NH<sub>4</sub>[C<sub>6</sub>H<sub>5</sub>N(O)NO]. The anion binds to metal cations through the two oxygen atoms, forming five-membered chelate rings.
Cupferron is prepared from phenylhydroxylamine and an NO<sup>+</sup> source:
Being a bidentate mono-anionic ligand, CU<sup>âÂÂ</sup> forms complexes analogous to those produced with acetylacetonate. Illustrative complexes include Cu(CU)<sub>2</sub>, Fe(CU)<sub>3</sub>, and Zr(CU)<sub>4</sub>.