Interaction between dioxoruthenium(VI) porphyrins and hydroxylamines: Coordination of N-substituted hydroxylamine to ruthenium and X-ray crystal structures of ruthenium complexes with a unidentate nitrosoarene ligand

Abstract

The interactions between dioxoruthenium(VI) porphyrins 1 with N-phenylhydroxylamine or unsubstituted hydroxylamine are described. Reaction of complexes 1 with excess PhNHOH leads to isolation of bis(nitrosobenzene)ruthenium(II) porphyrins 3 and mono(nitrosobenzene)ruthenium(II) porphyrins 4. Both the types of ruthenium complexes are characterized by 1H NMR, IR, and UV/Vis spectroscopy, and mass spectrometry. The X-ray structure determinations on [Ru II(TPP)(Ph-NO) 2] (3a), [Ru II(2,6-Cl-TPP)(PhNO) 2] (3e), and [Ru II(4-MeO-TPP)(PhNO)-(PhNH 2)] (4d) (TPP = tetraarylporphyrin) disclose a unidentate nitrosoarene coordination in all these complexes, with Ru-N(PhNO) bond lengths of 2.003(3) (3a, average), 1.991(3) (3e, average), and 2.042(2) Å (4d). In the case of 4d, the Ru-N(PhNH 2) bond length is found to be 2.075(3) Å. Mechanistic investigations reveal the formation of intermediates [Ru II(Por)(Ph-NO)(PhNHOH)] (5; Por = porphyrin), a ruthenium complex with N-substituted hydroxylamine ligand, in the "1 + PhNHOH" system. The Ru-NH-(OH)Ph moiety in 5 undergoes no rapid exchange with free PhNHOH in solution at room temperature, as revealed by 1H NMR spectroscopy. Unlike the interaction between complexes 1 and PhNHOH, reaction of such complexes with NH 2OH affords nitrosylruthenium(n) porphyrins [Ru II(Por)(NO)(OH)] (6). © WILEY-VCH Verlag GmbH, 2001.