4906-22-3Relevant articles and documents
Catalytic applications of CuII-containing MOFs based on N-heterocyclic ligand in the oxidative coupling of 2,6-dimethylphenol
Xiao, Bo,Hou, Hongwei,Fan, Yaoting
, p. 2014 - 2020 (2007)
Two CuII complexes bearing a N-heterocyclic ligand, namely [Cu(SO4)(pbbm)]n (1) and {[Cu(Ac)2(pbbm)] · CH3OH}n (2) (pbbm = 1,1′-(1,5-pentanediyl)bis-1H-benzimidazole) have been synthesized with the aim of exploiting new and potent catalysts. Single crystal X-ray diffraction shows that new polymeric complex 1 features 1-D double-chain framework. The catalytic studies on 1 and 2 indicate that they are efficient homogeneous catalysts for the oxidative coupling of 2,6-dimethylphenol (DMP) to poly(1,4-phenylene ether) (PPE) and diphenoquinone (DPQ) with H2O2 as oxidant and NaOMe as co-catalyst at room temperature. Optimal reaction conditions are obtained by examining the effects of solvent, the reaction time, temperature as well as the amounts of co-catalyst, catalyst and oxidant. Under the optimal conditions, the selectivity to PPE is almost up to 90% for both complexes, and the conversion of DMP is 85% for 1 and 90% for 2, comparable to those observed for highly active catalyst systems in the literature. Further comparison of their catalytic performances with those of the corresponding copper salt together with organic ligand, copper salt alone and free ligand reveals that the coordination of ligand to CuII ion plays a key role in generating the superior reactivities of complexes.
Activation of Molecular Oxygen. Mechanistic Studies of the Oxidation of Hindered Phenols with Cobalt-Dioxygen
Zombeck, Alan,Drago, Russell S.,Corden, Barry B.,Gaul, John H.
, p. 7580 - 7585 (1981)
Mechanistic studies of the oxidation of various substituted phenols by cobalt(II) bis(3-(salicylideneamino)propyl)methylamine, CoSMDPT, are reported.The reaction is first order in , , and .A series of experiments are reported to provide strong support for a mechanistic scheme that involves reaction of coordinate dioxygen.Coordination of O2 to this cobalt(II) complex enhances the ability of the dioxygen to abstract hydrogen atoms and to react with phenoxy radicals.The mechanism provides a rationale for the influence of several variables on the reaction and suggests steps that were taken to retard catalyst deactivation.
Preparation and Catalytic Oxidizing Potential of Polymer Supported Chelating Amine and Schiff Base Complexes
Drago, Russell S.,Gaul, John,Zombeck, Alan,Straub, Darel K.
, p. 1033 - 1038 (1980)
A new, versatile, high-yield synthesis for covalently attaching multidentate chelates to polystyrene is described.Polymeric substrates containing bound polydentate amines as discrete units can be obtained by reacting chloromethylated polystyrene with bis(2-cyanoethyl)amine, followed by BH3/THF reduction, to provide polymer-attached bis(3-aminopropyl)amine, (*)-DPT.These materials form the basis for the preparation of a wide variety of chelating ligands, for example, through the Schiff base reaction with various aldehydes and ketones.In order to demonstrate the feasibility of these polymer reactions, the entire sequence of reactions was carried out in solution using benzyl chloride as the starting material.A series of polymer-bound metal complexes were prepared and characterized.ESR spectra of the polymer-bound CuIISalDPT and CoIISalDPT*O2 complexes were very similar to their respective frozen glass spectra.The Moessbauer spectrum of the polymer-bound FeIISalDPT was similar to the powder spectrum.The Fe(II)-bound complex was irreversibly oxidized upon exposure to air.The CoIISalDPT-bound complex was found to be an active catalyst for the oxidation of 2,6-dimethylphenol.A large enhancement in product selectivity is obtained with the polymer Co(II) complex over the solution analogue.
Synthesis, magnetic behaviour, and X-ray structures of dinuclear copper complexes with multiple bridges. Efficient and selective catalysts for polymerization of 2,6-dimethylphenol
Murugavel, Ramaswamy,Pothiraja, Ramasamy,Gogoi, Nayanmoni,Clerac, Rodolphe,Lecren, Lollita,Butcher, Ray J.,Nethaji, Munirathinam
, p. 2405 - 2410 (2007)
The use of a potentially tridentate mono-anionic bridging ligand, 1,3-bis(3,5-dimethylpyrazol-1-yl)propan-2-ol (bdmpp-H), in assembling new dimeric copper complexes with interesting magnetic properties has been investigated. The reaction of copper hydroxide or copper acetate with phenyl phosphinic acid or diphenyl phosphinic acid in the presence of bdmpp-H produces the dinuclear complexes [Cu(bdmpp)(ppi)]2 (1) and [Cu(bdmpp)(dppi-H)]2(dppi)2 (2) (ppi-H = phenylphosphinic acid; dppi-H = diphenylphosphinic acid), respectively. The products have been characterized with the help of analytical, thermal, and spectroscopic (IR, UV-vis, and EPR) techniques. Single crystal X-ray diffraction studies of 1 and 2 reveal that the two bdmpp ligands hold together the dimeric copper unit in each complex through -O alkoxide and the pyrazolyl nitrogen ligating centers. Two phenyl phosphinate ligands additionally bridge the dicopper core in 1 to result in octahedral coordination geometry around each metal ion. The diphenyl phosphinic acid acts as a terminal ligand in 2, and thus completes a square pyramidal geometry around each copper ion. Both complexes show a very short Cu...Cu separation (3.001 and 3.065 A for 1 and 2, respectively). The investigation of the magnetic properties reveals the efficiency of the double alkoxide bridge between the two paramagnetic copper ions to mediate strong antiferromagnetic interactions [J/kB = -620(5) K (-431(4) cm -1) and -685(5) K (-476(4) cm-1) for 1 and 2, respectively]. Compounds 1 and 2, along with a few other copper phosphate complexes, were tested as catalysts for the oxidative polymerization of 2,6-dimethylphenol; 1 and 2 were found to be efficient catalysts with an increased selectivity for the formation of the polyphenylene ether. However a related mononuclear octahedral copper complex [Cu(imz)4(dtbp) 2] (dtbp-H = di-tert-butylphosphate) was found to be more efficient. The Royal Society of Chemistry.
Studies in peroxidase action-XVII. Some general observations
Saunders,Stark
, p. 1867 - 1872 (1967)
The peroxidase system oxidizes, 2,6-dimethylphenol and 2,6-dimethoxyphenol smoothly to the corresponding tetrasubstituted diphenoquinones; by contrast 2,6-dichlorophenol and 2,4,6-trichlorophenol given intractable products believed to result from the hydr
Hydrothermal syntheses of metal-organic frameworks constructed from aromatic polycarboxylate and 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl
Mu, Yajuan,Fu, Junhong,Song, Yajing,Li, Zhen,Hou, Hongwei,Fan, Yaoting
, p. 2183 - 2193 (2011)
Six new metal-organic frameworks, namely, {[Co(btmb)(HBTC)]?2H 2O}n (1), {[Co3(btmb)3(BTC) 2(H2O)2]?6H2O}n (2), {[Co3(btmb)3(BTC)2(H2O) 4]?2H2O}n (3), {[Ni3(btmb) 3(BTC)2(H2O)4]?2H 2O}n (4), [Cu(btmb)(HBTC)]n (5), and [Cu(btmb)(NDC)]n (6) (H3BTC = 1,3,5-benzenetricarboxylic acid, H2NDC = 1,2-benzenedicarboxylic acid, and btmb = 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl), have been synthesized under hydrothermal conditions. The structure of 1 is a 6-connected self-penetrating three-dimensional (3D) framework with 44?610?8 topology. Complex 2 exhibits a trinodal (3,4)-connected topology with a Schlaefli symbol of (62?84)(64? 82)(63). Both complexes 3 and 4 possess 3D pillar-layered structures with a Schlaefli symbol of (62?8?10 3)(64?8?10)(6?102). Complex 5 is also a 3D polymer with a pillar-layered framework, which can be simplified as the (63)(69?8) topology. Complex 6 shows a 4-connected 3D framework with a Schlaefli notation of (65?8) 2. Furthermore, complexes 1-6 as heterogeneous catalysts were studied in the green catalysis process of the oxidative coupling of 2,6-dimethylphenol (DMP) to poly(1,4-phenylene ether) (PPE) and diphenoquinone (DPQ). The results show that these complexes exhibit different catalytic activities; both the Cu complexes are catalytically active by showing high conversion of DMP and high selectivity of PPE, and they exhibit great potential as recyclable catalysts.
Syntheses, crystal structures of a series of copper(II) complexes and their catalytic activities in the green oxidative coupling of 2,6-dimethylphenol
Zhang, Erpeng,Hou, Hongwei,Han, Huayun,Fan, Yaoting
, p. 1927 - 1937 (2008)
Three mixed-ligand CuII complexes bearing iminodiacetato (ida) and N-heterocyclic ligands, namely, [Cu2(ida)2(bbbm)(H2O)2] · H2O (1), [Cu2(ida)2(btx)(H2O)2] · 2H2O (2) and [Cu2(ida)2(pbbm)(H2O)2] · H2O · 3CH3OH (3) (bbbm = 1,1′-(1,4-butanediyl)bis-1H-benzimidazole, btx = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene, pbbm = 1,1′-(1,3-propanediyl)bis-1H-benzimidazole), in addition to three fcz-based CuII complexes, namely, {[Cu(fcz)2(H2O)2] · 2NO3}n (4), {[Cu(fcz)2(H2O)] · SO4 · DMF · 2CH3OH · 2H2O}n (5) and {[Cu(fcz)2Cl2] · 2CH3OH}n (6) (fcz = 1-(2,4-difluorophenyl)-1,1-bis[(1H-1,2,4-triazol-l-yl) methyl]ethanol) have been prepared according to appropriate synthetic strategies with the aim of exploiting new and potent catalysts. Single crystal X-ray diffraction shows that 1 and 2 possess similar binuclear structures, 3 features a 2D pleated network, and 4 exhibits a 1D polymeric double-chain structure. Complexes 1-6 are tested as catalysts in the green catalysis process of the oxidative coupling of 2,6-dimethylphenol (DMP). Under the optimized reaction conditions, these complexes are catalytically active by showing high conversion of DMP and high selectivity of PPE. The preliminary study of the catalytic-structural correlations suggests that the coordination environment of the copper center have important influences on their catalytic activities.
Depolymerization of poly(2,6-dimethyl-1,4-phenylene oxide) under oxidative conditions
Saito, Kei,Masuyama, Toru,Oyaizu, Kenichi,Nishide, Hiroyuki
, p. 4240 - 4246 (2003)
Depolymerization of an engineering plastic, poly(2,6-dimethyl-1, 4-phenylene oxide) (PPO), was accomplished by using 2,6-dimethylphenol (DMP) under oxidative conditions. The addition of an excess amount of DMP to a solution of PPO in the presence of a CuCl/pyridine catalyst yielded oligomeric products. When PPO (Mn = 1.0 × 104, M w/Mn = 1.2) was allowed to react with a sufficient amount of DMP, the molecular weight of the product decreased to Mn = 4.9 × 102 (Mw/Mn = 1.5). By a prolonged reaction with the oxidant, the oligomeric product was repolymerized to produce PPO essentially identical to the starting material, making the oligomer useful as a reusable resource. During the depolymerization reaction, an intermediate phenoxyl radical was observed by ESR spectroscopy. Kinetic analysis showed that the rate of the oxidation of PPO was about 10 times higher than that of DMP. These results show that a monomeric phenoxyl radical attacks the polymeric phenoxyl to induce the redistribution via a quinone ketal intermediate, leading to the substantial decrease in the molecular weight of PPO, which is much faster than the chain growth.
Laccase initiated C-C couplings: Various techniques for reaction monitoring
Engelmann, Claudia,Illner, Sabine,Kragl, Udo
, p. 1591 - 1599 (2015)
In this study the fungal laccase from Myceliophthora thermophila (Novozym 51003) was investigated for oxidative C-C couplings of phenolic compounds. This enzyme requires only molecular oxygen as oxidant, which represents a great advantage for oxidative coupling reactions. However, such couplings are typically considered as highly unselective, due to the radical reaction mechanism of laccases. Based on different analytical techniques we gained detailed insights into laccase initiated coupling reactions. A preselection of potential substrates was realized via oxygen measurement during laccase initiated oxidations. Furthermore in situ FT-IR spectroscopy facilitated analyses in-depth, due to feasibility to detect dissolved as well as solid compounds. This technique allowed the detection of the grade of couplings of various laccase substrates, depending on different conditions. As a result oxidative dimerizations of 2,6-disubstituted phenols could be identified as highly selective and were scaled-up to multigram scale. Thereby the oxidation product of 2,6-diisopropyl phenol can be easily reduced to the corresponding biphenol, the antibacterial agent dipropofol. The presented techniques open up new biocatalytical approaches receiving quinoid units as key elements of many natural compounds and pharmaceuticals.
Carboxylic-supported copper complexes as catalyst for the green oxidative coupling of 2,6-dimethylphenol: Synthesis, characterization and structure
Liu, Qi,Wu, Huai Guang
, p. 451 - 461 (2013)
Three new Cu(II) complexes with carboxylic ligand, namely {[Cu(qc) 2(py)]·4H2O}∞ (1), [Cu(qc) 2(4,4′-bpy)]∞ (2) and [Cu(pc)(2,2′-bpy) (H2O)]2·H2O (3) (Hqc = 3-hydroxy-2-quinoxalinecarboxylic acid, H2pc = 4-hydroxyphthalic acid, py = pyrazine) have been synthesized and characterized. In both 1 and 2, each Cu(II) ion is coordinated by two quinoxalinecarboxylate moieties in the equatorial plane and two 4,4′-bpy or pyrazine units provide coordination in the axial positions, thus, resulting in a 1-D polymeric chain structure. Complex 3 has a dimeric structure in which two Cu(II) cations are bridged by two deprotonated pc2- ligands and two 2,2′-bpy molecules. As heterogeneous catalysts, the title complexes showed high catalytic efficiency in the green oxidative polymerization of 2,6-dimethylphenol (DMP) to poly(1,4-phenylene ether) (PPE) in the presence of H2O2 as oxidant in water under mild conditions. Moreover, they allow reuse without significant loss of activity through four runs, which suggests that these catalysts are efficient, mild, and easily recyclable for the oxidative coupling of DMP. The preliminary study of the catalytic-structural correlations suggests that the coordination environment of the metal center plays an important role in the improvement of their catalytic efficiencies.
