6390-69-8Relevant articles and documents
Copper(II) complexes of piperazine-derived tetradentate ligands and their chiral diazabicyclic analogues for catalytic phenol oxidative C-C coupling
Castillo, Ivan,Pérez, Viridiana,Monsalvo, Iván,Demare,Regla, Ignacio
, p. 1 - 4 (2013)
Reaction of the chiral ligands (1S,4S)-2,5-bis(6-methylpyridyl)- diazabicyclo[2.2.1]heptane (L1) and (1S,4S)-2,5-bis(1-methyl-2- methylbenzimidazolyl)-diazabicyclo[2.2.1]heptane (L2) with CuCl 2 results in the hydroxo-bridged dicopper complexes [(L 1)Cu2(μ-OH)(H2O)Cl3] (3), and [(L2)Cu2(μ-OH)(H2O)Cl3] (4). Both chiral complexes were characterized spectroscopically, and 3 in the solid state by X-ray crystallography, confirming they are structurally related to their previously reported copper acetate analogues (1 and 2) due to their hydroxo-bridged bimetallic core. The achiral ligand analogues N,N′-bis(2-picolyl)piperazine (L3) and N,N′-bis(1-methyl- 2-methylbenzimidazolyl)piperazine (L4) were employed to obtain the corresponding complexes with CuCl2, affording the chloro-bridged [(L3)(CuCl)2(μ-Cl)2]n (5) and [(L4)(CuCl)2(μ-Cl)2] (6), neither of which features a bridging hydroxo ligand; instead, complex 5 was structurally characterized as a coordination polymer. The acetate-derived complexes 1 and 2 are active in oxidative C-C coupling of 2,4-di-tert-butylphenol, while 3 and 4 have low activity; the achiral complexes 5 and 6, lacking a bridging hydroxo ligand, are inactive in this reaction.
Bismuthanes as Hemilabile Donors in an O2-Activating Palladium(0) Complex
Materne, Karolin,Braun-Cula, Beatrice,Herwig, Christian,Frank, Nicolas,Limberg, Christian
, p. 11797 - 11801 (2017)
A xanthene-based bismuthane/phosphane chelating ligand has been accessed that has enabled the synthesis of a palladium(0) bismuthane complex. The bismuthane donor proved to be hemilabile as it switched to a dangling position upon addition of O2 that gave a palladium(II) peroxide complex. Unlike the corresponding 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) palladium peroxide, the bismuth analogue could be employed for catalytic phosphane oxidation and oxidative phenol coupling.
Unprecedented direct cupric-superoxo conversion to a bis-μ-oxo dicopper(III) complex and resulting oxidative activity
Quist, David A.,Ehudin, Melanie A.,Karlin, Kenneth D.
, p. 155 - 161 (2019)
Investigations of small molecule copper-dioxygen chemistry can and have provided fundamental insights into enzymatic processes (e.g., copper metalloenzyme dioxygen binding geometries and their associated spectroscopy and substrate reactivity). Strategically designing copper-binding ligands has allowed for insight into properties that favor specific (di)copper-dioxygen species. Herein, the tetradentate tripodal TMPA-based ligand (TMPA = tris((2-pyridyl)methyl)amine) possessing a methoxy moiety in the 6-pyridyl position on one arm (OCH3TMPA) was investigated. This system allows for a trigonal bipyramidal copper(II) geometry as shown by the UV–vis and EPR spectra of the cupric complex [(OCH3TMPA)CuII(OH2)](ClO4)2. Cyclic voltammetry experiments determined the reduction potential of this copper(II) species to be ?0.35 V vs. Fc+/0 in acetonitrile, similar to other TMPA-derivatives bearing sterically bulky 6-pyridyl substituents. The copper-dioxygen reactivity is also analogous to these TMPA-derivatives, affording a bis-μ-oxo dicopper(III) complex, [{(OCH3TMPA)CuIII}2(O2?)2]2+, upon oxygenation of the copper(I) complex [(OCH3TMPA)CuI](B(C6F5)4) at cryogenic temperatures in 2-methyltetrahydrofuran. This highly reactive intermediate is capable of oxidizing phenolic substrates through a net hydrogen atom abstraction. However, after bubbling of the precursor copper(I) complex with dioxygen at very low temperatures (?135 °C), a cupric superoxide species, [(OCH3TMPA)CuII(O2[rad]?)]+, is initially formed before slowly converting to [{(OCH3TMPA)CuIII}2(O2?)2]2+. This appears to be the first instance of the direct conversion of a cupric superoxide to a bis-μ-oxo dicopper(III) species in copper(I)-dioxygen chemistry.
Oxidant-Controlled Catalytic Transformations of Phenols with Unexpected Cleavage of Aromatic Rings
Li, Wei,Song, Feijie,You, Jingsong
, p. 13913 - 13918 (2015)
Oxidative transformations of phenols have attracted significant attention of chemists due to their importance in biological process and organic synthesis. In contrast to the relatively well-developed oxygenation and coupling reactions of phenols, the highly efficient and selective oxidative ring cleavage of phenols is under-represented. This work describes a novel CuCl-catalyzed tandem homocoupling/skeletal rearrangement of phenols that realizes the cleavage of the phenol ring by using air or Ag2CO3 as the oxidant. Interestingly, simply changing the oxidant to K2S2O8 results in the oxidative coupling/cyclization of phenols to give dibenzofurans. These results set an important precedent of oxidant-controlled catalytic transformations of phenols.
Activation of a high-valent manganese-oxo complex by a nonmetallic lewis acid
Baglia, Regina A.,Duerr, Maximilian,Ivanovic-Burmazovic, Ivana,Goldberg, David P.
, p. 5893 - 5895 (2014)
The reaction of a manganese(V)-oxo porphyrinoid complex with the Lewis acid B(C6F5)3 leads to reversible stabilization of the valence tautomer MnIV(O)(π-radical cation). The latter complex, in combination with B(C6F5)3, reacts with ArO-H substrates via formal hydrogen-atom transfer and exhibits dramatically increased reaction rates over the MnV(O) starting material.
A Bis(μ-oxido)dinickel(III) Complex with a Triplet Ground State
Morimoto, Yuma,Takagi, Yusaku,Saito, Toru,Ohta, Takehiro,Ogura, Takashi,Tohnai, Norimitsu,Nakano, Motohiro,Itoh, Shinobu
, p. 7640 - 7643 (2018)
A bis(μ-oxido)dinickel(III) complex was synthesized and characterized by single crystal X-ray diffraction, resonance Raman, and ESI-mass measurements. Magnetic susceptibility measurements by SQUID and EPR spectroscopy reveal that the complex has a triplet ground state, which is unprecedented for high-valent metal (M) complexes with [M2(μ-O)2] diamond core. DFT studies indicate ferromagnetic coupling of the nickel(III) centers. The complex exhibits hydrogen abstraction reactivity and oxygenation reactivity toward external substrates.
Influence of ligand architecture on oxidation reactions by high-valent nonheme manganese oxo complexes using water as a source of oxygen
Barman, Prasenjit,Vardhaman, Anil Kumar,Martin, Bodo,W?rner, Svenja J.,Sastri, Chivukula V.,Comba, Peter
, p. 2095 - 2099 (2015)
Mononuclear nonheme MnIV=O complexes with two isomers of a bispidine ligand have been synthesized and characterized by various spectroscopies and density functional theory (DFT). The MnIV=O complexes show reactivity in oxidation reactions (hydrogen-atom abstraction and sulfoxidation). Interestingly, one of the isomers (L1) is significantly more reactive than the other (L2), while in the corresponding FeIV=O based oxidation reactions the L2-based system was previously found to be more reactive than the L1-based catalyst. This inversion of reactivities is discussed on the basis of DFT and molecular mechanics (MM) model calculations, which indicate that the order of reactivities are primarily due to a switch of reaction channels (σ versus π) and concomitant steric effects.
Copper(i) complexes based on ligand systems with two different binding sites: Synthesis, structures and reaction with O2
Li,Braun-Cula,Hoof,Limberg
, p. 544 - 560 (2018)
The synthesis of the ligand systems L1 and L2 with two different N3-binding sites linked through a dibenzofuran spacer and their coordination properties towards a variety of CuI precursors are reported. The reaction of L1 with copper halides leads to the formation of a bimetallic species [(L1)(CuICl)2] (1), and metallodimers [((L1)(CuIX)2)2(μ-(CuI2)(μ-X)2)] (2: X = Br, 3: X = I) in which two dicopper complexes are bridged by a (μ-(CuI2)(μ-X)2)-moiety whereas L2 reacts with copper chloride to afford {[CuI2(L2)Cl2]}n (8). Furthermore, starting from L1 in combination with copper(i) salts of weakly coordinating anions the dicopper complexes [(L1)(CuI(NCCH3))2](BF4)2 (4), [(L1)(CuI(NCCH3))(Cu(Y))](Y) (5: Y = OTf, 6: Y = ClO4) and [(L1)(CuI2(dppe))](PF6)2 (7) were isolated, and employing L2, the complexes [(L2)(CuI(NCCH3))2](Z)2 (9: Z = PF6, 10: Z = OTf) and [(L2)(CuI2(dppe))](PF6)2 (11) were obtained. Complexes 4-6 as well as 9 and 10 react rapidly with O2 to form metastable O2 adducts in acetone at -90 °C, where O2 is bound between the two copper centers within one dicopper molecule, as evidenced by UV/Vis spectroscopy, kinetic investigations, Raman spectroscopy and studies with ligands containing the isolated donor sites. The reactivity of the O2 adducts towards selected substrates was also investigated, showing their ability to act as electrophiles as well as nucleophiles.
Direct Resonance Raman Characterization of a Peroxynitrito Copper Complex Generated from O2 and NO and Mechanistic Insights into Metal-Mediated Peroxynitrite Decomposition
Liu, Jeffrey J.,Siegler, Maxime A.,Karlin, Kenneth D.,Mo?nne-Loccoz, Pierre
, p. 10936 - 10940 (2019)
We report the formation of a new copper peroxynitrite (PN) complex [CuII(TMG3tren)(κ1-OONO)]+ (PN1) from the reaction of [CuII(TMG3tren)(O2.?)]+ (1) with NO.(g) at ?125 °C. The first resonance Raman spectroscopic characterization of such a metal-bound PN moiety supports a cis κ1-(?OONO) geometry. PN1 transforms thermally into an isomeric form (PN2) with κ2-O,O′-(?OONO) coordination, which undergoes O?O bond homolysis to generate a putative cupryl (LCuII?O.) intermediate and NO2.. These transient species do not recombine to give a nitrato (NO3?) product but instead proceed to effect oxidative chemistry and formation of a CuII–nitrito (NO2?) complex (2).
Oxidation of 2,4-Di-t-butylphenol with Hydrogen Peroxide Catalyzed by Bis(ethylenediamine)copper(II) Complex
Kushioka, Keiko,Tanimoto, Iwao,Maruyama, Kazuhiro
, p. 1147 - 1153 (1989)
2,4-Di-t-butylphenol (1) was efficiently oxidized with H2O2 in methanol in the presence of bis(ethylenediamine)copper(II) (Cu(II)(en)2 complexes.Activity of the Cu(II) complexes was strongly dependent on the structure of the en ligands, as in the cases of the O2 oxidation of phenol I.In the H2O2 oxidation of I, ens having none of N-alkyl substituent were of the most efficient.By addition of H2O2, stable Cu(II)(en)2 complexes exhibited a new absorption at 340 nm, which was assigned to Cu(II)-en-H2O2 (1:2:1) complexes.Furthermore, the rapid-scanning spectrophotometry proved that quadruple Cu(II)-en-phenol 1-H2O2 (1:1:1) complexes were the key intermediate for the oxidation of 1.The initial velocity can be summarized in the equation υ = k.The oxidation mechanism of phenol I with H2O2 is proposed.
