Oxidation of a nitronyl nitroxide by copper(II) ions: synthesis and X-ray diffraction characterization of 4,4,5,5-tetramethyl-1-oxo-2-phenyl-4,5-dihydroimidazolium perchlorate N(3)-oxide

In contrast to most transition-metal salts, copper perchlorate in acetonitrile oxidizes the nitronyl nitroxide radical (1) to the corresponding nitrosonium perchlorate (2) which is easily isolated in very good yield. Although more stable than the dialkyl analogues and thus easier to handle, this compound has all the oxidizing properties known for nitrosonium cations. Compound (2) has been characterized the X-ray diffraction. The structural data show equivalent N[double bond, length half m-dash]O bond lengths of 1.225(4)Å and will be of great value in determining the oxidation state of the NO group in structurally characterized nitroxyl-metal complexes.