Interaction between Dioxoruthenium(VI) Porphyrins and Hydroxylamines: Coordination ofN-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)(PhNO)2] (3a), [Ru(II)(2,6-Cl-TPP)(PhNO)2] (3e), and [Ru(II)(4-MeO-TPP)(PhNO)(PhNH2)] (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) A (4d). In the case of 4d, the Ru-N(PhNH2) bond length is found to be 2.075(3) A. Mechanistic investigations reveal the formation of intermediates [Ru(II)(Por)(PhNO)(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 NH2OH affords nitrosylruthenium(II) porphyrins [Ru(II)(Por)(NO)(OH)] (6).

Nitrido Ruthenium Porphyrins: Synthesis, Characterization, and Amination Reactions with Hydrocarbon or Silyl Enol Ethers

“…Ruthenium porphyrins constitute an unmatched family of metalloporphyrin that exhibits extraordinary versatility in binding N‐donating ligands at the axial sites 1–5. A wide variety of ruthenium porphyrins featuring axial RuN bonds have been prepared, including those bearing amine,1c, 3a,3b amido,3b–d,g imido,3a,c–e,g,j imine,3h, 4 methyleneamido,3h nitrile,1a, 2 hydrazido,3f nitrosoarene,1b, 3i nitrosyl,5 and dinitrogen1d axial ligands (Scheme , a – j ). This makes the lack of isolable ruthenium porphyrins with terminal nitrido axial ligands (Scheme 1, k ) especially conspicuous 6.…”

Tuning the Reactivity of Dioxoruthenium(VI) Porphyrins toward an Arylimine by Altering Porphyrin Substituents

“…Since the first synthesis of [Ru VI (TMP)O 2 ] (TMP = meso -tetramesitylporphyrinato dianion) by Groves and Quinn in 1984,1a dioxoruthenium(VI) porphyrins, [Ru VI (Por)O 2 ], have received considerable attention. − This interesting family of high-valent ruthenium porphyrins not only exhibits high reactivity toward oxidation of hydrocarbons, 1b,2b-f,,,,,, thioethers,4a alcohols,4b and phosphines, 4d,9a,b but also serves as unique precursors for preparation of amine, 4c,9d,e,17a-c nitrosoarene,17f hydroxylamine,17f amido, 17b,c hydrazido(1−),17d and imido 17c complexes of ruthenium porphyrins.…”

Cerium(IV) Sulfate as a Cocatalyst for Promoting the Direct Epoxidation of Propylene by Ruthenium Porphyrin with Molecular Oxygen

“…As shown in Figure , the Soret band underwent a 4 nm blue-shift, accompanied by a similar blue-shift in the Q-band. Such changes in the UV–vis spectra have been attributed to the generation of oxidatively active Ru IV O species during epoxidation. − …”