53177-12-1Relevant articles and documents
Towards Catalytic Ammonia Oxidation to Dinitrogen: A Synthetic Cycle by Using a Simple Manganese Complex
Keener, Megan,Peterson, Madeline,Hernández Sánchez, Raúl,Oswald, Victoria F.,Wu, Guang,Ménard, Gabriel
supporting information, p. 11479 - 11484 (2017/08/30)
Oxidation of the nucleophilic nitride, (salen)Mn≡N (1) with stoichiometric [Ar3N][X] initiated a nitride coupling reaction to N2, a major step toward catalytic ammonia oxidation (salen=N,N'-bis(salicylidene)-ethylenediamine dianion; Ar=p-bromophenyl; X=[SbCl6]? or [B(C6F5)4]?). N2 production was confirmed by mass spectral analysis of the isotopomer, 1-15N, and the gas quantified. The metal products of oxidation were the reduced MnIII dimers, [(salen)MnCl]2 (2) or [(salen)Mn(OEt2)]2[B(C6F5)4]2 (3) for X=[SbCl6]? or [B(C6F5)4]?, respectively. The mechanism of nitride coupling was probed to distinguish a nitridyl from a nucleophilic/electrophilic coupling sequence. During these studies, a rare mixed-valent MnV/MnIII bridging nitride, [(salen)MnV(μ-N)MnIII(salen)][B(C6F5)4] (4), was isolated, and its oxidation-state assignment was confirmed by X-ray diffraction (XRD) studies, perpendicular and parallel-mode EPR and UV/Vis/NIR spectroscopies, as well as superconducting quantum interference device (SQUID) magnetometry. We found that 4 could subsequently be oxidized to 3. Furthermore, in view of generating a catalytic system, 2 can be re-oxidized to 1 in the presence of NH3 and NaOCl closing a pseudo-catalytic “synthetic” cycle. Together, the reduction of 1→2 followed by oxidation of 2→1 yield a genuine synthetic cycle for NH3 oxidation, paving the way to the development of a fully catalytic system by using abundant metal catalysis.
Effect of substituents on the Mn(III)Salen catalyzed oxidation of styrene
Zsigmond,Horvath,Notheisz
, p. 95 - 102 (2008/10/08)
The influence of the electron-donating tert-butyl group both on the encapsulation of the Salen ligand and the catalytic activity of the catalyst produced was studied. Styrene oxidation at room temperature and 1 atm using molecular oxygen as oxidant and tert-butyl hydroperoxide as initiator showed that neat and encapsulated Mn(III)Salen complexes (Br2Salen and (tert-butyl)4Salen) were active. Using the intrazeolite ligand synthesis (or template synthesis) method, the increase in the size of the complexes improved their physical entrapping in the zeolite. The encapsulation produced more stable catalysts, especially in the case of (tert-butyl)4Salen catalyst.
Stepwise, metal-assisted decarboxylation promoted by manganese: Reactivity relationship between manganese and vanadium
Li, Xinhua,Pecoraro, Vincent L.
, p. 3403 - 3410 (2008/10/08)
Manganese(III) complexes of the ligand ethylenebis[(o-hydroxyphenyl)glycine], Mn(EHPG)-, are shown to oxidatively decarboxylate in methanol, DMF, and acetone solutions to generate derivatives of [ethylenebis(salicylideneaminato)]manganese(III), Mn(SALEN)+. This process occurs via air oxidation of MnIII(EHPG)- to form MnIV(EHPG), which subsequently loses CO2 and one proton, forming [N-(2-(o-salicylideneamino)ethyl)(o-hydroxyphenyl)glycinato]manganese(III), MnIII(EHGS). MnIII-(EHGS) is also air sensitive and will further decarboxylate to MnIII(SALEN)+. When this reaction is completed in acetone, X-ray-quality crystals of MnIII(SALEN)[2-(3-oxobutenyl)phenolate] are recovered. This very loosely associated solid-state dimer contains a rare example of monodentate phenolate coordination to Mn(III). The generation of MnIII(SALEN)+ has been followed by electrochemistry and paramagnetic NMR spectroscopy. MnIII(EHPG)- shows an oxidative wave in methanol with E0 = +450 mV and in DMF with E0 = +300 mV (vs SCE). Bulk electrolysis at +600 mV in methanol quantitatively (by the passage of four electrons) generates MnIII(SALEN)+, which has an Mn(III)/Mn(II) reduction at -250 mV. The paramagnetic NMR spectrum, of a mixture of rac and meso isomers of MnIII(EHPG)- in CD3OD shows resonances at +26.3, -18.6 and -34.6 ppm (rac isomer) and +27.8, +24.0, -2.4, -16.5, -22.5, -32.5, and -35.5 ppm (meso isomers). After 9 days, the spectrum of MnIII(SALEN)+ has developed completely with resonances at -4.1, -23.2, and -28.9 ppm. MnIII(EHGS) is not produced in sufficient quantities to be detected under these conditions. In contrast, DMF solutions of MnIII(EHPG)- (shifts at +27.3, +24.8, -2.4, -18.0, -21.6, -32.0, and -35.5 ppm, meso isomer) slowly form MnIII(EHGS) with features at +45.6, +28.6, +13.1 -9.4, -19.5, and -27.7 ppm, and ultimately one recovers MnIII(SALEN)+ with peaks at +29.5, -2.4, -22.3, and -25.4 ppm. In contrast, the FeIII(EHPG)-, CuII(EHPG)2-, and GaIII(EHPG)- complexes are air stable. This metal-assisted, oxidative decarboxylation is analogous to that previously described for VVO(HEHPG), which was shown to generate V(III) species as intermediates. Therefore, this facile decarboxylation reaction appears to be promoted by using ions that can cycle through three oxidation states and suggests that a cycle for the manganese-facilitated process includes both Mn(IV) and Mn(II) X-ray parameters for MnIII(SALEN)[2-(3-oxobutenyl)phenolate]: MnC26H23N2O4, mol wt 482.4, monoclinic (P21/c), a = 12.200 (4) ? b = 14.104 (4) ?, c = 13.584 (3) ?, β = 103.74 (2)°, V = 2270 (1) ?3, Z = 4, 3503 unique data collected with 0 3σ(I). The best model gave R = 0.044 and Rw = 0.039.
