88301-26-2Relevant academic research and scientific papers
Electronic Structure and Multicatalytic Features of Redox-Active Bis(arylimino)acenaphthene (BIAN)-Derived Ruthenium Complexes
Singha Hazari, Arijit,Ray, Ritwika,Hoque, Md Asmaul,Lahiri, Goutam Kumar
, p. 8160 - 8173 (2016/08/24)
The article examines the newly designed and structurally characterized redox-active BIAN-derived [Ru(trpy)(R-BIAN)Cl]ClO4 ([1a]ClO4-[1c]ClO4), [Ru(trpy)(R-BIAN)(H2O)](ClO4)2 ([3a](ClO4)2-[3c](ClO4)2), and BIAO-derived [Ru(trpy)(BIAO)Cl]ClO4 ([2a]ClO4) (trpy = 2,2′:6′,2′′-terpyridine, R-BIAN = bis(arylimino)acenaphthene (R = H (1a+, 3a2+), 4-OMe (1b+, 3b2+), 4-NO2 (1c+, 3c2+), BIAO = [N-(phenyl)imino]acenapthenone). The experimental (X-ray, 1H NMR, spectroelectrochemistry, EPR) and DFT/TD-DFT calculations of 1an-1cn or 2an collectively establish {RuII-BIAN0} or {RuII-BIAO0} configuration in the native state, metal-based oxidation to {RuIII-BIAN0} or {RuIII-BIAO0}, and successive electron uptake processes by the α-diimine fragment, followed by trpy and naphthalene π-system of BIAN or BIAO, respectively. The impact of the electron-withdrawing NO2 function in the BIAN moiety in 1c+ has been reflected in the five nearby reduction steps within the accessible potential limit of -2 V versus SCE, leading to a fully reduced BIAN4- state in [1c]4-. The aqua derivatives ({RuII-OH2}, 3a2+-3c2+) undergo simultaneous 2e-/2H+ transfer to the corresponding {RuIV-O} state and the catalytic current associated with the RuIV/RuV response probably implies its involvement in the electrocatalytic water oxidation. The aqua derivatives (3a2+-3c2+) are efficient and selective precatalysts in transforming a wide variety of alkenes to corresponding epoxides in the presence of PhI(OAc)2 as an oxidant in CH2Cl2 at 298 K as well as oxidation of primary, secondary, and heterocyclic alcohols with a large substrate scope with H2O2 as the stoichiometric oxidant in CH3CN at 343 K. The involvement of the {RuIV-O} intermediate as the active catalyst in both the oxidation processes has been ascertained via a sequence of experimental evidence.
Tunable Electrochemical and Catalytic Features of BIAN- and BIAO-Derived Ruthenium Complexes
Hazari, Arijit Singha,Das, Ankita,Ray, Ritwika,Agarwala, Hemlata,Maji, Somnath,Mobin, Shaikh M.,Lahiri, Goutam Kumar
, p. 4998 - 5012 (2015/05/27)
This article deals with a class of ruthenium-BIAN-derived complexes, [RuII(tpm)(R-BIAN)Cl]ClO4 (tpm = tris(1-pyrazolyl)methane, R-BIAN = bis(arylimino)acenaphthene, R = 4-OMe ([1a]ClO4), 4-F ([1b]ClO4), 4-Cl ([1c]ClO4), 4-NO2 ([1d]ClO4)) and [RuII(tpm)(OMe-BIAN)H2O]2+ ([3a](ClO4)2). The R-BIAN framework with R = H, however, leads to the selective formation of partially hydrolyzed BIAO ([N-(phenyl)imino]acenapthenone)-derived complex [RuII(tpm)(BIAO)Cl]ClO4 ([2]ClO4). The redox-sensitive bond parameters involving -N=C-C=N- or -Ni=C-C=O of BIAN or BIAO in the crystals of representative [1a]ClO4, [3a](PF6)2, or [2]ClO4 establish its unreduced form. The chloro derivatives 1a+-1d+ and 2+ exhibit one oxidation and successive reduction processes in CH3CN within the potential limit of ±2.0 V versus SCE, and the redox potentials follow the order 1a+ + + + ≈ 2+. The electronic structural aspects of 1an-1dn and 2n (n = +2, +1, 0, -1, -2, -3) have been assessed by UV-vis and EPR spectroelectrochemistry, DFT-calculated MO compositions, and Mulliken spin density distributions in paramagnetic intermediate states which reveal metal-based (RuII → RuIII) oxidation and primarily BIAN- or BIAO-based successive reduction processes. The aqua complex 3a2+ undergoes two proton-coupled redox processes at 0.56 and 0.85 V versus SCE in phosphate buffer (pH 7) corresponding to {RuII-H2O}/{RuIII-OH} and {RuIII-OH}/{RuIV=O}, respectively. The chloro (1a+-1d+) and aqua (3a2+) derivatives are found to be equally active in functioning as efficient precatalysts toward the epoxidation of a wide variety of alkenes in the presence of PhI(OAc)2 as oxidant in CH2Cl2 at 298 K, though the analogous 2+ remains virtually inactive. The detailed experimental analysis with the representative precatalyst 1a+ suggests the involvement of the active {RuIV=O} species in the catalytic cycle, and the reaction proceeds through the radical mechanism, as also supported by the DFT calculations.
Autoxidation of Vinylcyclopentane, Vinylcyclohexane, and 4-Vinylcyclohex-1-ene
Biela, R.,Bilas, W.,Ihsan, U.,Pritzkow, W.,Schmidt-Renner, W.
, p. 893 - 900 (2007/10/02)
The title olefins were oxidized with molecular oxygen at 75-80 deg C.About 40percent of the oxygen absorbed were found by iodometric titration as peroxidic oxygen.The reaction products were analyzed by a combination of chemical methods, gas chromatography, and 13C-n.m.r.-spectroscopy.Vinylcyclopentane and vinylcyclohexane are attacked preferably at the tertiary allylic C-H-bonds giving almost equimolar mixtures of the corresponding allylisomeric hydroperoxides.In the case of 4-vinylcyclohex-1-ene the C-H-bonds in position 6 are preferably attacked, but products of attack on the other allylic C-H-bonds also could be identified.In all cases the amount of products which could not be detected gaschromatographically was determined by balance experiments in the presence of an internal standard.
