Electronic structure of the oxidation catalyst cis(bipyridine)oxo(pyridine) ruthenium(IV) diperchlorate

Dobson, J. C.; Helms, Jeffrey H.; Doppelt, P.; Sullivan, B. Patrick; Hatfield, William E.; Meyer, Thomas J.

doi:10.1021/ic00310a037

Cited by 41 publications

(34 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the basis of magnetic susceptibility measurements, the oxoruthenium(IV) complexes 1a − e (μ eff ∼ 2.9μ B ) have a triplet electronic ground state: a [(d xy ) 2 (d xz ) 1 (d yz ) 1 ] configuration. Studies by Meyer and co-workers revealed that a very small activation barrier of 56 cm -1 exists for conversion to a singlet excited state; therefore, a rapid triplet−singlet interconversion is expected in solution at room temperature . The singlet [Ru IV O] 1 species was believed to behave like an oxene: a priori and able to effect concerted oxygen atom insertion to alkene, whereas the triplet [Ru IV O] 3 form would react via a stepwise radical pathway.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Investigation of the Oxidation of Aromatic Alkenes by Monooxoruthenium(IV). Asymmetric Alkene Epoxidation by Chiral Monooxoruthenium(IV) Complexes

Fung

Ming

1998

J. Org. Chem.

View full text Add to dashboard Cite

The oxoruthenium(IV) complexes [RuIV(terpy)(6,6‘-Cl2-bpy)O](ClO4)2 (1a; terpy = 2,2‘:6‘,2‘ ‘-terpyridine; 6,6‘-Cl2-bpy = 6,6‘-dichloro-2,2‘-bipyridine), [RuIV(terpy)(tmeda)O](ClO4)2 (1b; tmeda = N,N,N‘,N‘-tetramethylethylenediamine), [RuIV(Cn)(bpy)O](ClO4)2 (1c; Cn = 1,4,7-trimethyl-1,4,7-triazacyclononane), and [RuIV(PPz*)(bpy)O](ClO4)2 (1d; PPz* = 2,6-bis[(4S,7R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-4,7-methanoindazol-2-yl]pyridine) are effective for the epoxidation of aromatic alkenes in acetonitrile at ambient conditions. Their reactions with cis-alkenes such as cis-β-methylstyrene and cis-β-deuteriostyrene afford epoxides nonstereospecifically. The observation of the inverse secondary kinetic isotope effect for the β-d 2-styrene oxidations [k H/k D = 0.87 (1b), 0.86 (1d)], but not for α-deuteriostyrene (k H/k D = 0.98 for 1b and 1d), indicates that C−O bond formation is more advanced at the β-carbon atom than at the α carbon, i.e., a stepwise mechanism. The second-order rate constants (k 2) for the styrene oxidations are weakly dependent on the E°(RuIV/III) values of the oxoruthenium(IV) complexes, and both electron-withdrawing and -donating para substituents mildly accelerate the oxidation reaction of styrene. These findings discount strongly the intermediaries of an alkene-derived cation radical and a carbocation. A linear free-energy relationship between the second-order rate constants for the para-substituted styrene oxidations and the total substituent effect (TE) parameters has been established: ρTE • = +0.43 (R = 0.99) for 1b, +0.50 (R = 0.98) for 1c, and +0.37 (R = 0.99) for 1d (Wu, Y.-D.; Wong, C.-L.; Chan, K. W.; Ji, G.-Z.; Jiang, X.-K. J. Org. Chem. 1996, 61, 746). This suggests that the oxidation of aromatic alkenes by oxoruthenium(IV) complexes should proceed via the rate-limiting formation of a benzylic radical intermediate. Oxidation of styrene and cis- and trans-β-methylstyrenes by the chiral oxoruthenium(IV) complex 1d attains moderate enantioselectivities, in which the production of cis-epoxide is more enantioselective than the trans counterpart. The ligand dissymmetry of PPz* together with the bipyridine ligand create a “chiral pocket” around the RuIVO moiety, leading to enantiofacial discrimination through nonbonding interaction. Because the acyclic benzylic radical intermediate would undergo cis−trans isomerization before the second C−O bond formation, the overall product enantioselectivity (% eeobs) cannot be determined exclusively by facial selectivity (eefacial) of the first irreversible C−O bond formation step. The extent of the isomerization, measured by the cis−trans-epoxide selectivity or diastereoselectivity of epoxide ring closure, is an important element in controlling the enantiomeric excess of the epoxides.

show abstract

Section: Resultsmentioning

confidence: 99%

Mechanistic Investigation of the Oxidation of Aromatic Alkenes by Monooxoruthenium(IV). Asymmetric Alkene Epoxidation by Chiral Monooxoruthenium(IV) Complexes

Fung

Ming

1998

J. Org. Chem.

View full text Add to dashboard Cite

show abstract

“…7), exhibiting, however, a diffusion limited pattern, suggesting the occurrence of a relatively slow electron-transfer through the porphyrin material. In addition, both processes are expected to be proton dependent, i.e., leading to Ru III -OH and Ru IV @O species, with the release of one and two protons, respectively, by analogy with the literature [8][9][10][11][12][13][14][15][16][17][18].…”

Section: Electrochemical Properties Of the Supramolecular Filmsmentioning

confidence: 87%

“…High-valence transition metal-oxo complexes, such as the manganese and iron porphyrins [1][2][3][4][5][6][7], and the oxo-ruthenium polypyridines [8][9][10][11][12][13][14][15][16][17][18], have been studied with great interest as oxygen atom transfer catalysts. The cis-[Ru(bipy) 2 (py)O] 2þ species (bipy, 2,2 0 -bipyridine; py, pyridine), for instance, is known to be an efficient catalyst for oxidation of organic and inorganic substrates, performing also DNA oxidation and cleavage either by activation of the 1 0 -ribose C-H bond or by oxo transfer to the guanine nucleobase [19][20][21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Enhanced electrochemical and electrocatalytic activity of a new supramolecular manganese-porphyrin species containing four bis(bipyridine)(aqua)ruthenium(II) complexes

Araki

Winnischofer

Viana

et al. 2004

Journal of Electroanalytical Chemistry

View full text Add to dashboard Cite

“…(2) A six-coordinate Ru(IV)-oxo complex should be in the S = 1 spin state and thus should be paramagnetic. [82][83][84][85][86] The well-resolved spectra shown in Fig. 3 and 8 disclosed that the Ru(IV) complexes should be sevencoordinate in the S = 0 spin state with a coordination structure as cis-[Ru(IV)vO(bpy) 2 Cl 2 ].…”

Section: Reaction Mechanismmentioning

confidence: 99%

Synergistic oxygen atom transfer by ruthenium complexes with non-redox metal ions

Zheng

Chen

et al. 2016

Dalton Trans.

View full text Add to dashboard Cite

Non-redox metal ions can affect the reactivity of active redox metal ions in versatile biological and heterogeneous oxidation processes; however, the intrinsic roles of these non-redox ions still remain elusive. This work demonstrates the first example of the use of non-redox metal ions as Lewis acids to sharply improve the catalytic oxygen atom transfer efficiency of a ruthenium complex bearing the classic 2,2'-bipyridine ligand. In the absence of Lewis acid, the oxidation of ruthenium(ii) complex by PhI(OAc)2 generates the Ru(iv)[double bond, length as m-dash]O species, which is very sluggish for olefin epoxidation. When Ru(bpy)2Cl2 was tested as a catalyst alone, only 21.2% of cyclooctene was converted, and the yield of 1,2-epoxycyclooctane was only 6.7%. As evidenced by electronic absorption spectra and EPR studies, both the oxidation of Ru(ii) by PhI(OAc)2 and the reduction of Ru(iv)[double bond, length as m-dash]O by olefin are kinetically slow. However, adding non-redox metal ions such as Al(iii) can sharply improve the oxygen transfer efficiency of the catalyst to 100% conversion with 89.9% yield of epoxide under identical conditions. Through various spectroscopic characterizations, an adduct of Ru(iv)[double bond, length as m-dash]O with Al(iii), Ru(iv)[double bond, length as m-dash]O/Al(iii), was proposed to serve as the active species for epoxidation, which in turn generated a Ru(iii)-O-Ru(iii) dimer as the reduced form. In particular, both the oxygen transfer from Ru(iv)[double bond, length as m-dash]O/Al(iii) to olefin and the oxidation of Ru(iii)-O-Ru(iii) back to the active Ru(iv)[double bond, length as m-dash]O/Al(iii) species in the catalytic cycle can be remarkably accelerated by adding a non-redox metal, such as Al(iii). These results have important implications for the role played by non-redox metal ions in catalytic oxidation at redox metal centers as well as for the understanding of the redox mechanism of ruthenium catalysts in the oxygen atom transfer reaction.

show abstract

Electronic structure of the oxidation catalyst cis(bipyridine)oxo(pyridine) ruthenium(IV) diperchlorate

Cited by 41 publications

References 0 publications

Mechanistic Investigation of the Oxidation of Aromatic Alkenes by Monooxoruthenium(IV). Asymmetric Alkene Epoxidation by Chiral Monooxoruthenium(IV) Complexes

Mechanistic Investigation of the Oxidation of Aromatic Alkenes by Monooxoruthenium(IV). Asymmetric Alkene Epoxidation by Chiral Monooxoruthenium(IV) Complexes

Enhanced electrochemical and electrocatalytic activity of a new supramolecular manganese-porphyrin species containing four bis(bipyridine)(aqua)ruthenium(II) complexes

Synergistic oxygen atom transfer by ruthenium complexes with non-redox metal ions

Contact Info

Product

Resources

About