- Oxo Transfer from Nitrogen Dioxide to Nitrito Group in a Copper(II) Complex
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Reaction of Cu(II) complex [CuII(LH)(O2CCH3)2] (1) [LH = 4,6-ditert-butyl-2-((2-picolyl(isopropyl)amino)methyl)phenol] with equivalent amount of NO2 leads to the reduction of Cu(II) to Cu(I) with concomitant nitration at the phenol ring of the ligand. This resulted in the in situ formation of intermediate Cu(I) complex of the nitrated ligand (L′H). Additional equivalent of NO2 coordinates to the Cu(I) complex to form corresponding O-nitrito Cu(II) complex [CuII(L′(η1-ONO)] (2). Subsequent addition of NO2 led to the corresponding O-nitrato complex, [CuII(L′)(η1-ONO2)] (3) with concomitant formation of NO. Complexes 2 and 3 were isolated and structurally characterized. The formation of NO in the reaction was established by spin-trapping experiment. Isotopic labeling experiment revealed that the oxo transfer takes place from NO2 to the coordinated η1-ONO group.
- Gogoi, Kuldeep,Deka, Hemanta,Kumar, Vikash,Mondal, Biplab
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- Synthesis and characterization of aminopyridine iron(ii) chloride catalysts for isoprene polymerization: Sterically controlled monomer enchainment
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In this study, a series of 2-R-6-(1-(alkylamino)methyl)pyridine-iron complexes [alkyl: (CPh3) Fe1H; (CHPh2) Fe2H; (CHPh2) Fe3Me; (CHMePh) Fe4H; (CH2Ph) Fe5H; (CHMe2) Fe6H; (C6H11) Fe7H; (CH2(4-OMe)Ph) Fe8H; (CH2(4-CF3)Ph) Fe9H; (CH2(2,4,6-Me3)Ph) Fe10H; (CH2Ph) Fe11Me] were synthesized and well characterized by ATR-IR spectroscopy, HRMS spectroscopy and elemental analysis. In addition, Fe3Me, Fe4H, Fe7H and Fe11Me were characterized by X-ray diffraction analysis: Fe3Me and Fe11Me adopted distorted tetrahedral geometries in the solid state while Fe4H and Fe7H were found in dimeric or polymeric forms respectively in which chlorides acted as bridging ligands. The catalytic capacities of these iron complexes were investigated for isoprene polymerization. Upon activation with a MAO cocatalyst, the catalytic activities of complexes varied as a function of the steric and electronic influences of substituents. In general, the catalysts bearing the least steric groups and electron-withdrawing groups exhibited relatively high activities. An outstanding activity of 190.6 × 104 g·mol-1·h-1 was obtained by Fe5H [CH2Ph]. Moreover, changes in the steric hindrance around the metal center showed a notable effect on the selectivity of monomer enchainment. In particular, most of the polymers obtained by these complexes bearing flexible frameworks were in favor of 3,4-enchainment.
- Jing, Chuyang,Wang, Liang,Mahmood, Qaiser,Zhao, Mengmeng,Zhu, Guangqian,Zhang, Xianhui,Wang, Xiaowu,Wang, Qinggang
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p. 7862 - 7874
(2019/06/13)
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- Cyclopentadienyl-Ru(II)-Pyridylamine Complexes: Synthesis, X-ray Structure, and Application in Catalytic Transformation of Bio-Derived Furans to Levulinic Acid and Diketones in Water
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A series of cationic half-sandwich cyclopentadienyl-ruthenium(II)-pyridylamine complexes, [(η5-C5H5)Ru(κ2-L)(PPh3)]+ (L = Namine-substituted pyridylamine ligands) ([Ru]-1-[Ru]-6), along with the analogous cyclopentadienyl-ruthenium(II)-N-isopropylpyridylimine complex [(η5-C5H5)Ru(κ2-L)(PPh3)]+ (L = N-isopropylpyridylimine) ([Ru]-7), have been synthesized in good yields. Structural identities of all the complexes have been authenticated by 1H, 13C, and 31P NMR, mass spectrometry, and X-ray crystallography. The synthesized complexes exhibited high catalytic activity for the transformation of the bio-derived furans, 2-furfural (furfural), 5-methyl-2-furfural (5-MF), and 5-hydroxymethyl-2-furfural (5-HMF) to levulinic acid (LA) and the diketones, 3-hydroxyhexane-2,5-dione (3-HHD), 1-hydroxyhexane-2,5-dione (1-HHD), and hexane-2,5-dione (HD) in water. Efficient transformation of furfural to LA over a range of η5-Cp-Ru-pyridylamine complexes is substantially affected by the Namine-substituents, where a η5-Cp-Ru-N-propylpyridylamine complex ([Ru]-2) exhibited higher catalytic activity in comparison to other η5-Cp-Ru-pyridylamine and η5-Cp-Ru-pyridylimine complexes. The relative catalytic activity of the studied complexes demonstrated a substantial structure-activity relationship which is governed by the basicity of Namine, steric hindrance at Namine, and the hemilabile nature of the coordinated pyridylamine ligands.
- Dwivedi, Ambikesh D.,Sahu, Vinod K.,Mobin, Shaikh M.,Singh, Sanjay K.
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supporting information
p. 4777 - 4787
(2018/04/25)
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- Synthesis, structures of (aminopyridine)nickel complexes and their use for catalytic ethylene polymerization
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A series of α-aminopyridines in the form of (2,6-C6H 3N)(R1)(CHR2NR3R4) (R1 = R2 = H R3 = H R4 = iPr (L1a), R4 = tBu (L1b), R4 = Ph (L1c), R4 = 2,6-Me2C6H3 (L1d), R4 = 2,6-iPr2C6H3 (L1e), R1 = R2 = H R3 = R4 = Et (L1f), R1 = H R2 = Me R3 = H R4 = iPr (L2a), R4 = Ph (L2c), R4 = 2,6-Me 2C6H3 (L2d), R4 = 2,6- iPr2C6H3 (L2e), R1 = Me R2 = H R3 = H R4 = 2,6-iPr 2C6H3 (L3e)) and β-aminopyridines in the form of (2-C6H4N)(CH2CH2NR 1R2) (R1 = H R2 = iPr (4a), R2 = tBu (L4b), R1 = R2 = Et (L4f)) have been prepared. Their corresponding halonickel complexes 1a-4f are synthesized by ligand substitution from (DME)NiBr2 and the molecular structures are characterized. Four types of coordination modes include four-coordinate mononuclear species with one ligand, five-coordinate mononuclear species with two ligands, five-coordinate dinuclear species with two ligands, and a six-coordinate polymeric framework were determined by X-ray crystallography. Using methylaluminoxanes (MAO) as the activator, the nickel complexes can catalyze ethylene polymerization under moderate pressure and ambient temperature. The activity reaches 105 g PE mol-1 Ni h. The PE products with high branching and high crystallinity have M n ~ 103 with PDI 2.
- Lin, Ya-Chi,Yu, Kuo-Hsuan,Lin, Ya-Fan,Lee, Gene-Hsiang,Wang, Yu,Liu, Shiuh-Tzung,Chen, Jwu-Ting
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scheme or table
p. 6661 - 6670
(2012/08/08)
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- N-heterocyclic pyridylmethylamines: Synthesis, complexation, molecular structure, and application to asymmetric Suzuki-Miyaura and oxidative coupling reactions
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The synthesis of N,N-bidentate ligands based on a π-deficient N-heterocyclic pyridylmethylamine core is described. The preparation and characterization of the corresponding N,N-ligand-palladium complexes in solution and the solid state are illustrated. Pd complexes showed a good yield and moderate catalytic activity (up to 40% ee) in the asymmetric Suzuki-Miyaura coupling reaction, leading to methoxybinaphthyl derivatives. The combination of N,N-pyridylmethylamines with cuprous iodide revealed effective catalytic systems in oxidative naphthol derivative coupling reactions, affording the corresponding binaphthyls in high yields and with enantioselectivities of up to 61%.
- Grach, Guillaume,Pieters, Gregory,Dinut, Aurelia,Terrasson, Vincent,Medimagh, Raouf,Bridoux, Alexandre,Razafimahaleo, Vanessa,Gaucher, Anne,Marque, Sylvain,Marrot, Jerome,Prim, Damien,Gil, Richard,Planas, Jose Giner,Vinas, Clara,Thomas, Isabelle,Roblin, Jean-Philippe,Troin, Yves
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scheme or table
p. 4074 - 4086
(2011/10/03)
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- Unsymmetrical dizinc complexes as models for the active sites of phosphohydrolases
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The unsymmetrical dinucleating ligand 2-(N-isopropyl-N-((2-pyridyl)methyl) aminomethyl)-6-(N-(carboxylmethyl)-N-((2-pyridyl)methyl)aminomethyl) -4-methylphenol (IPCPMP or L) has been synthesized to model the active site environment of dinuclear metallohydrolases. It has been isolated as the hexafluorophosphate salt H4IPCPMP(PF6)2· 2H2O (H4L), which has been structurally characterized, and has been used to form two different Zn(ii) complexes, [{Zn2(IPCPMP) (OAc)}2][PF6]2 (2) and [{Zn2(IPCPMP) (Piv)}2][PF6]2 (3) (OAc = acetate; Piv = pivalate). The crystal structures of 2 and 3 show that they consist of tetranuclear complexes with very similar structures. Infrared spectroscopy and mass spectrometry indicate that the tetranuclear complexes dissociate into dinuclear complexes in solution. Potentiometric studies of the Zn(ii):IPCPMP system in aqueous solution reveal that a mononuclear complex is surprisingly stable at low pH, even at a 2:1 Zn(ii):L ratio, but a dinuclear complex dominates at high pH and transforms into a dihydroxido complex by a cooperative deprotonation of two, probably terminally coordinated, water molecules. A kinetic investigation indicates that one of these hydroxides is the active nucleophile in the hydrolysis of bis(2,4-dinitrophenyl)phosphate (BDNPP) enhanced by complex 2, and mechanistic proposals are presented for this reaction as well as the previously reported transesterification of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) promoted by Zn(ii) complexes of IPCPMP.
- Jarenmark, Martin,Csapo, Edit,Singh, Jyoti,Woeckel, Simone,Farkas, Etelka,Meyer, Franc,Haukka, Matti,Nordlander, Ebbe
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experimental part
p. 8183 - 8194
(2011/01/07)
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- Multicomponent reaction of imidazo[1,5- a ]pyridine carbenes with aldehydes and dimethyl acetylenedicarboxylate or allenoates: A straightforward approach to fully substituted furans
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The facile three-component reactions of N,N-substituted imidazo[1,5-a]pyridine carbenes, namely imidazo[1,5-a]pyridin-3-ylidenes, with aldehydes and DMAD or allenoates were disclosed. Both reactions proceeded via tandem nucleophilic addition, [3 + 2]-cycloaddition, and ring transformation to produce different 4-[(2-pyridyl)methyl]aminofuran derivatives generally in moderate yields. This work not only 'rovided the first example of the application of imidazo[1,5-a]pyridin-3-ylidenes in organic synthesis but also developed a straightforward approach to fully substituted furans that are not easily accessible by other methods.
- Pan, Huan-Rui,Li, Yong-Jia,Yan, Cai-Xia,Xing, Juan,Cheng, Ying
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supporting information; experimental part
p. 6644 - 6652
(2010/11/17)
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- Alternating ethylene-norbornene copolymerization catalyzed by cationic organopalladium complexes bearing hemilabile bidentate ligands of α-amino-pyridines
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Cationic methylpalladium complexes with hemilabile bidentate ligands of α-amino-pyridines, in the form of {[R1HNCR2H(o- C6H5N)]Pd(Me)(NCMe)}(BF4) (R1 = iPr, tBu, Ar R2 = H, Me) have been found to be effective precursors for catalytic copolymerization of ethylene and norbornene under mild conditions. The copolymer products exhibit predominant alternating microstructures which are evidenced by NMR and mass spectrometry as well as a kinetic analysis according to the Finman-Ross relationship.
- Lin, Ya-Chi,Yu, Kuo-Hsuan,Huang, Shou-Ling,Liu, Yi-Hung,Wang, Yu,Liu, Shiuh-Tzung,Chen, Jwu-Ting
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supporting information; experimental part
p. 9058 - 9067
(2010/03/30)
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- Symmetrical and unsymmetrical dizinc complexes as models for the active sites of hydrolytic enzymes
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Dinuclear carboxylate-bridged zinc complexes of one symmetric and one asymmetric phenolate-based ligand catalyse the transesterification of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) at different rates, with an unsymmetrical complex being more active than a symmetric one. The Royal Society of Chemistry.
- Jarenmark, Martin,Kappen, Sascha,Haukka, Matti,Nordlander, Ebbe
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p. 993 - 996
(2008/09/20)
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- General and environmentally friendly synthesis of heterocyclic multidentate molecules based on microwave-assisted heating protocol
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An efficient microwave heating methodology for the synthesis of heterocyclic multidentate molecules is reported. Each compound was obtained with high yield and purity in a few minutes from easily available starting materials such as amines, heteroaldehydes and N-hydroxymethyl pyrazoles or triazoles. In addition, this approach allows synthesis without any solvent or organic and inorganic by-products.
- Regnier, Thomas,Lavastre, Olivier
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p. 155 - 159
(2007/10/03)
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- Calix[4]arenes Linked to Multiple Bidentate N-Donors: Potential Ligands for Synthetic Modeling of Multinuclear Metalloenzymes
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(Matrix Presented) A series of calix[4]arenes incorporating three or four bidentate diamines or pyridylamines attached at the upper rim were synthesized via practical protocols. Proof of structure was obtained in one instance by X-ray crystallography. These molecules are designed for general use as ligands for the preparation of multinuclear active site models of metalloenzymes.
- Spencer, Douglas J. E.,Johnson, Bryan J.,Johnson, Brian J.,Tolman, William B.
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p. 1391 - 1393
(2007/10/03)
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- Compounds with Bridgehead Nitrogen 52 -NMR Spectra and Stereochemistry of the 2-Alkylperhydroimidazolopyridines
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In contrast to perhydro-oxazolopyridine and perhydrothiazolopyridine, which adopt equilibria in CDCl3 solution at room temperature containing ca 70percent trans-fused conformers in equilibria with O- or S-inside cis-fused conformers, 2-alkylperhydroimidazolopyridines are found to adopt equilibria containing >98percent trans-fused conformers.Comparison of NMR parameters of 2-methylperhydroimidazolopyridine with those of the two isomers of 1,2-dimethylperhydroimidazolopyridine indicates an equilibrium for the former compound between the two trans-fused conformers, with ca 83percent of that conformation containing a transarrangement of nitrogen lone pairs of electrons.These observations are explained in terms of the generalized anomeric effect.KEY WORDS Perhydroimidazolopyridine Conformational equilibria 1H and 13C NMR
- Banting, Lee,Crabb, Trevor A.
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p. 696 - 706
(2007/10/02)
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