- Epoxidation of cyclohexene with O2 and isobutyraldehyde catalysed by cobalt modified hydrotalcites
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The paper presents a comparison between the catalytic performances of cobalt modified hydrotalcites obtained from different cobalt precursors in the epoxidation of cyclohexene using molecular oxygen, isobutyraldehyde as reductant, at 25 °C and 1 atmosphere pressure of oxygen in acetonitrile as solvent. Two different types of cobalt containing catalysts were prepared - (i) a hydrotalcite-like compound containing cobalt in the brucite type layer, CoMg/Al, and (ii) three catalysts obtained by impregnation of the as-synthesized hydrotalcite support (HT) with CoCl2, bis-triphenylphosphine-dichlorocobalt (II) Co P(C6H5)32Cl2, (A), and an admixture of complexes (AB) containing bis-triphenylphosphine-dichlorocobalt (II) Co P(C6H5)32Cl2 (A) and benzyltriphenyl phosphonium-tetrachlorocobaltate C6H5CH2P(C6H5) 32+ CoCl42- (B). The names of these catalysts have been abbreviated as CoCl2/HT, A/HT and AB/HT. The catalysts were characterized by chemical analyses, DR-UV-vis, DRIFTS, XRD, EDX and texture measurements. The most active and selective catalyst was AB/HT. A linear correlation between the ratio Cl/Co in the resulting solids and the yield to epoxide has been established. For AB precursor the effect of the support has been also investigated using as carriers the mixed oxide CHT derived from the calcination of the parent hydrotalcite, and the reconstructed hydrotalcite RHT obtained by rehydration of CHT.
- Angelescu,Ionescu,Pavel,Zǎvoianu,B?rjega,Luculescu,Florea,Olar
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- Catalytic one-pot three-component synthesis of 3,3′-disubstituted oxindoles and spirooxindole pyrans by mixed ligand transition metal complexes
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Abstract: New three-component reaction was developed via one-pot strategy for the synthesis of functionalized 3,3′-disubstituted oxindoles and spirooxindole through the reaction among isatin, malononitrile, and acetone/indole/nitromethane/acetylacetone/di
- Hegade, Sujit,Gaikwad, Gautam,Jadhav, Yuvraj,Pore, Avinash,Mulik, Abhijeet
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- Mixed ligand cobalt and palladium complexes containing triphenylphosphine and a hydrazone: Synthesis and application in non-linear optics
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Mixed ligand complexes of cobalt and palladium containing triphenylphosphine and a hydrazone derived from furfural and hydrazine hydrate have been designed, synthesized, evaluated, and characterized from their spectral properties, elemental analysis, and magnetic susceptibility measurements. The spectral techniques suggest that the complexes exhibit square planar geometry. The monomeric properties of the complexes are evaluated from their magnetic susceptibility values. The complexes were subjected to z-scan analysis for third-order non-linear optical measurements. Non-linear transmission measurements performed using laser pulses at 532 nm in nanosecond indicate that the complexes may show good potential as optical limiters.
- Ramakrishna, Dileep
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p. 462 - 466
(2020/07/30)
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- Simpler and Cleaner Synthesis of Variously Capped Cobalt Nanocrystals Applied in the Semihydrogenation of Alkynes
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Unlike the classical organometallic approach, we report here a synthetic pathway requiring no reducing sources or heating to produce homogeneous hexagonal-close-packed cobalt nanocrystals (Co NCs). Involving a disproportionation process, this simple and fast (6 min) synthesis is performed at room temperature in the presence of ecofriendly fatty alcohols to passivate Co NCs. Through a recycling step, the yield of Co NCs is improved and the waste generation is limited, making this synthetic route cleaner. After an easy exchange of the capping ligands, we applied them as unsupported catalysts in the stereoselective semihydrogenation of alkynes.
- Moisset, A.,Petit, C.,Petit, M.,Salzemann, C.,Sodreau, A.,Vivien, A.
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supporting information
p. 13972 - 13978
(2020/10/09)
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- Alkene isomerization-hydroboration promoted by phosphine-ligated cobalt catalysts
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Generated in situ from air-stable cobalt precursors or readily synthesized using NaHBEt3, (PPh3)3CoH(N2) was found to be an effective catalyst for the hydroboration of alkenes. Unlike previous base-metal catalysts for alkene isomerization-hydroboration which favor the incorporation of boron at terminal positions, (PPh3)3CoH(N2) promotes boron incorporation adjacent to π-systems even in substrates where the alkene is at a remote position, enabling a unique route to 1,1-diboron compounds from α -dienes.
- Scheuermann, Margaret L.,Johnson, Elizabeth J.,Chirik, Paul J.
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supporting information
p. 2716 - 2719
(2015/06/16)
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- Solvent effect on cis-1,4-specific polymerization of 1,3-butadiene with CoCl2(PRPh2)2-EASC catalytic systems
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A series of phosphine-containing cobalt complexes [CoCl 2(PRPh2)2, R = Ph (1), Cy (2), nPr (3), Et (4), Me (5), H (6)] has been used for the highly active and stereospecific polymerization of 1,3-butadiene upon activation with ethylaluminum sesquichloride (EASC). The high catalytic activities and polybutadienes with high cis-1,4 selectivity were obtained in the solution polymerization in toluene. The conversion of butadiene and the microstructure and molecular weight of the resulting polymers were affected by reaction parameters and the R group on the phosphine ligand. The dispersion medium was also a sensitive factor for the current catalytic systems, influencing the catalytic activity and properties of products. In comparison with the solution polymerization in toluene, the heterogeneous polymerization in isooctane yielded slightly lower catalytic activity, cis-1,4 content and molecular weight under similar reaction conditions.
- Zhou, Qinzhuo,Li, Bo-Geng,Jie, Suyun,Zheng, Na
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p. 773 - 779
(2014/03/21)
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- Inspiration from old molecules: Field-induced slow magnetic relaxation in three air-stable tetrahedral cobalt(ii) compounds
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We have investigated the dynamics of the magnetization of three four-coordinate mononuclear cobalt(ii) compounds, which are synthesized conveniently and are air stable. Slow magnetic relaxation effects were observed for the compounds in the presence of a dc magnetic field. The Royal Society of Chemistry 2013.
- Yang, Fen,Zhou, Qi,Zhang, Yiquan,Zeng, Guang,Li, Guanghua,Shi, Zhan,Wang, Bingwu,Feng, Shouhua
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supporting information
p. 5289 - 5291
(2013/06/27)
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- Cobalt complexes in [EMIM]Cl - A catalyst for oxidation of alcohols to carbonyls
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A coordination complex system consisting of Cobalt (II)-Schiff bases with triphenylphosphine were synthesized and characterized. These catalysts were effective in the oxidation of primary and secondary alcohols. The oxidation reactions were carried out in ethyl-methyl-imidazolium ionic liquid in presence of NaOCl. Higher catalytic activity was observed for CoL1.
- Ramakrishna, Dileep,Ramachandra Bhat, Badekai
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p. 195 - 198
(2010/06/12)
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- Facile dichloromethane activation and phosphine methylation. Isolation of unprecedented zwitterionic organozinc and organocobalt intermediates
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Both C-Cl bonds of CH2Cl2 are readily activated by CoCl2 and metallic Zn allowing quantitative methylation of phosphines; unprecedented zwitterionic Co(ii) and Zn(ii) intermediates have been characterized which display α-m
- Pattacini, Roberto,Jie, Suyun,Braunstein, Pierre
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p. 890 - 892
(2009/07/10)
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- Complexes of functional phosphines. 23. PPh3 and β-ketophosphine complexes of cobalt(II). Crystal and molecular structures of CoCl2[Ph2PCH2C(O)Ph]2 and Co2(CO)6[Ph2PCH2C(O)Ph]2 and of the trinuclear, mixed-metal complex [(Ph3P)2 ...
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Full title: Complexes of functional phosphines. 23. PPh3 and β-ketophosphine complexes of cobalt(II). Crystal and molecular structures of CoCl2[Ph2PCH2C(O)Ph]2 and Co2(CO)6[Ph2PCH2C(O)Ph]2 and of the trinuclear, mixed-metal complex [(Ph3P)2Ag(μ-Cl)2Co(μ-Cl) 2Ag(PPh3)2]·0.5OEt2. The solution chemistry of cobalt(II) ketophosphine complexes CoX2[Ph2PCH2C(O)Ph]2 (1a, X = Cl; 1b, X = Br; 1c, X = I) has been examined and compared to that of [CoX2(PPh3)2] (2a, X = Cl; 2b, X = Br; 2c, X = I). All the complexes undergo a tetrahedral-octahedral equilibrium in methanol. This is facilitated by solvent coordination rather than by the ligand's keto functions. Some degree of ligand displacement also occurs. The crystal structure of 1a has been elucidated, showing a pseudotetrahedral cobalt(II) geometry. A long interligand hydrogen-bond, not present in powder samples, is observed between the methylene group of a Ph2PCH2C(O)Ph ligand and the ketone function of the other Ph2PCH2C(O)Ph ligand. 1a reacts with Na[Co(CO)4] to afford the crystallographically characterized, metal-metal bonded centrosymmetric complex Co2(CO)6[Ph2PCH2C(O)Ph]2 (5) (Co-Co = 2.666(1) A?). The reactivity of 1a with AgBF4 and TlPF6 has also been examined and compared to that of 2a where the latter is reacted in the presence and absence of excess phosphine. Notable reaction products include the square planar cobalt(II) complex [Co{Ph2PCH2C(O)Ph}{Ph2PCH 2C(O)Ph}Cl]PF6 (6), which slowly transforms in solution to the octahedral complex [Co{Ph2PCH2C(O)Ph}2{Ph2PCH 2C(O)Ph}Cl]PF6 (7). Reaction with AgBF4 under similar conditions affords the silver phosphine complex Ag{Ph2PCH2C(O)Ph}2Cl (8). 2a reacts with AgBF4 to give [Ag-(PPh3)2]BF4, but additionally in the presence PPh3 gives (Ph3P)2Ag(μ-Cl)2Co(μ-Cl) 2Ag(PPh3)2 (13). The latter formulation involving a central CoCl42- core, and an almost linear Ag-Co-Ag arrangement has been confirmed by single-crystal X-ray diffraction. The solid state structures of 1a, 5, and 13·0.5OEt2 have been determined by single-crystal X-ray analysis. 1a crystallizes in the monoclinic space group P21/c with Z = 4 in a unit cell of dimensions a = 10.985(2) A?, b = 17.236(4) A?, c = 19.547(4) A?, and β = 104.87(2)°. 5 crystallizes in the triclinic space group P1 with Z = 1, a = 8.916(2) A?, b = 11.177(7) A?, c = 12.009(4) A?, α = 81.15(5)°, β = 76.39(2)°, and γ = 67.47(3)°. Complex 13·0.5OEt2, crystallizes in the monoclinic space group P21/c with Z = 8, a = 21.840(5) A?, b = 17.664(6) A?, c = 36.890(7) A?, and β = 93.14(2)°.
- Braunstein, Pierre,Kelly, David G.,Dusausoy, Yves,Bayeul, Daniel,Lanfranchi, Maurizio,Tiripicchio, Antonio
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p. 233 - 242
(2008/10/08)
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- Homogeneous Isomerization of 1-Butene Catalyzed by -NaBH4 Systems (M=Co, Ni, X=Halides, SCN, PR3=PPhnEt3-n) - Acceleration by Phosphine Addition and Stereoselectivity
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The stoichiometric or a little excess amount of NaBH4 was treated with (M=Co, Ni, X=halides, SCN, PR3=PPhnEt3-n) in THF-1,2-dimethoxyethane to form monohydride species which were active for isomerization of 1-butene.The reaction was accelerated by excess PPh3 in -NaBH4 systems.Other catalytic systems have optimum ratios of excess phosphine to metal for getting maximum activities.Thiocyanate-metal complexes are the most active in each Co- and Ni-catalyst system.Cis-selectivity depends on the cone angle of PR3, the size of anion ligands, and the congested structure of the complexes.
- Kanai, Hiroyoshi,Sakai, Shigeyoshi,Sakatani, Takenobu
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p. 1589 - 1594
(2007/10/02)
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- DIMERISATION DE MONOOLEFINES CATALYSEE PAR DES COMPLEXES DU NICKEL ET DU COBALT GENERES ELECTROCHIMIQUEMENT
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Dimerization of olefins was performed with NiL2X2 and CoL2X2 complexes by an electrochemical reduction process under controlled cathodic potential.The influence of several parameters (choice of anode, supporting electrolyte, ligand, temperature and pressure) was studied in order to increase the dimer production and selectivity.In case of ethylene, with nickel-based catalysts, 2-butenes are formed selectively with a turn-over number of 12 000 within 50 h.With propylene as substrate methylpentenes are the main products, in which case the reaction rate appears to be two orders of magnitude lower than with ethylene under identical conditions.Although less active, cobalt based catalysts show an unusual behaviour, as they are particularly selective for 1-butene production (>90percent).
- Masotti, H.,Wallet, J. C.,Pfeiffer, G.
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p. 241 - 252
(2007/10/02)
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- The Electro-Syntheses of Anhydrous Metal Chloride Complexes of Iron, Cobalt, and Nickel
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The electro-syntheses of the anhydrous metal(II) chlorides od Fe, Co, and Ni are described.The appropriate metal is present in the form of a sacrificial anode and the reaction is carried out in an undivided cell with ethanolic solutions of hydrogen chloride.The primary products, MCl2 . n EtOH (1 - 3), are obtained in yields of 83 - 100percent based upon the current consumed and are converted into 4 - 6 upon reaction with THF, into 7 - 12 upon reaction with triorganophosphanes and into the tetrachlorometallate(II) complexes 13 - 15 upon reaction with Cl.Electrochemical reduction of nickel(II) chloride and triphenylphosphane (1 : 3) in THF leads to the formation of chlorotris(triphenylphosphane)nickel(I) (18) in 65percent yield.
- Lehmkuhl, Herbert,Mehler, Klaus,Hauschild, Gerlinde
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p. 438 - 444
(2007/10/02)
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