- Mononuclear nickel(II) dithiolate complexes with chelating diphosphines: Insight into protonation and electrochemical proton reduction
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Inspired by the metal active sites of [FeFe]- and [NiFe]?hydrogenases, a series of mononuclear Ni(II) ethanedithiolate complexes [{(Ph2PCH2)2×}Ni(SCH2CH2S)] (X = NCH2C5H4N-p (2a), NCH2C6H5 (2b), NCH2CHMe2 (2c), and CH2 (2d)) with chelating diphosphines were readily synthesized through the room-temperature treatments of mononuclear Ni(II) dichlorides [{(Ph2PCH2)2×}NiCl2] (1a-1d) with ethanedithiol (HSCH2CH2SH) in the presence of triethylamine (Et3N) as acid-binding agent. All the as-prepared complexes 1a-1d and 2a-2d are fully characterized through elemental analysis, nuclear magnetic resonance (NMR) spectrum, and by X-ray crystallography for 1b, 2a-2d. To further explore proton-trapping behaviors of this type of mononuclear Ni(II) complexes for catalytic hydrogen (H2) evolution, the protonation and electrochemical proton reduction of 2a-2c with aminodiphosphines (labeled PCNCP = (Ph2PCH2)2NR) and reference analogue 2d with nitrogen-free diphosphine (dppp = (Ph2PCH2)2CH2) are studied and compared under trifluoroacetic acid (TFA) as a proton source. Interestingly, the treatments of 2a-2d with excess TFA resulted in the unexpected formation of dinuclear Ni(II)-Ni(II) dication complexes [{(Ph2PCH2)2×}2Ni2(μ-SCH2CH2S)](CF3CO2)2 (3a-3d) and mononuclear Ni(II) N-protonated complexes [{(Ph2PCH2)2N(H)R}Ni(SCH2CH2S)](CF3CO2) (4a-4c), which has been well supported by high-resolution electrospray ionization mass spectroscopy (HRESI-MS), NMR (31P, 1H) as well as fourier transform infrared spectroscopy (FT-IR) techniques, and especially by X-ray crystallography for 3d. Additionally, the electrochemical properties of 2a-2d are investigated in the absence and presence of strong acid (TFA) by using cyclic voltammetry (CV), showing that the complete protonation of 2a-2d gave rise to dinuclear Ni2S2 species 3a-3d for electrocatalytic proton reduction to H2.
- Gu, Xiao-Li,Li, Jian-Rong,Li, Qian-Li,Guo, Yang,Jing, Xing-Bin,Chen, Zi-Bing,Zhao, Pei-Hua
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- Nickel-catalyzed electrocarboxylation of allylic halides with CO2
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Nickel-catalyzed regioselective electrocarboxylation of allylic halides with CO2at atmospheric pressure has been developed by adjusting reaction parameters, including catalyst, solvent, temperature and additive. β,γ-Unsaturated carboxylic acids were obtained in moderate to good yields and with high chain selectivity. This reaction shows tolerance to functional groups. In addition, cyclic voltammetry was performed to provide the possible mechanism of nickel-catalyzed CO2allylation.
- Wu, La-Xia,Deng, Fang-Jie,Wu, Lin,Wang, Huan,Chen, Tai-Jie,Guan, Ye-Bin,Lu, Jia-Xing
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p. 13137 - 13141
(2021/08/03)
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- Efficient catalytic transfer hydrogenation reactions of carbonyl compounds by Ni(II)-diphosphine complexes
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The catalytic transfer hydrogenation reactions of a series of aromatic and aliphatic carbonyl compounds were investigated using divalent Ni(II)-diphosphine complexes, [L2NiCl2] (where L2 = 1,1-bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,1-bis(diphenylphosphino)ferrocene (dppf), and N-butyl-N-(diphenylphosphino)-1,1-diphenylphosphinamine (dppba)). This is a single-step reaction in the presence of potassium hydroxide and isopropyl alcohol to afford the corresponding alcohols. This protocol tolerates other sensitive functional groups like olefinic double bonds and also achieves high chemoselectivity. All the reactions were monitored by GC and GC–MS. The plausible mechanism is also discussed. The method reported in the present article is simple, cost-effective, and provides excellent conversions. Nickel-diphosphine complexes appear as a potential alternative to expensive transition metal complexes.
- Venkatesh, Sadhana,Panicker, Rakesh R.,Lenin Kumar, Verdhi,Pavankumar,Viswanath, Nukala,Singh, Shangrila,Desikan, Rajagopal,Sivaramakrishna, Akella
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p. 2963 - 2977
(2020/11/03)
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- METHOD FOR PRODUCING SULFONYL CHLORIDE COMPOUND
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A process for producing a sulfonyl chloride compound comprising: (A) a step comprising reacting a pyridazine compound represented by the formula (1): wherein R1 represents a hydrogen atom, a halogen atom, an alkyl group which may be substituted with a halogen atom or atoms, or the like, R2 and R3 are the same or different and each represents a hydrogen atom or the like, R4 represent a hydrogen atom, a halogen atom, an alkyl group which may be substituted with a halogen atom or atoms, or the like, with a sulfonating agent; (B) a step comprising contacting the reaction mixture obtained in the step (A) with a chlorinating agent; and (C) a step comprising mixing the reaction mixture obtained in the step (B) with an aqueous inorganic base solution to separate an organic layer containing a sulfonyl chloride compound represented by the formula (2): wherein R1 to R4 are the same meanings as defined above.
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Page/Page column 8
(2008/12/06)
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- Process design and scale-up of the synthesis of 2,2′:5′,2′-terthienyl
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The objective of this study was the design of a scaleable process for the synthesis of 3-4 mol of α-terthienyl from 2,5-dibromothiophene and thienylmagnesium bromide in a 10-L stirred tank reactor. In THF the Grignard reagent, thienylmagnesium bromide, was readily formed from 2-bromothiophene and magnesium. To avoid crystallization the maximal concentration was limited to 1.4 M. Furthermore, the novel combination of THF and NiCl2[bis(diphenylphosphino)benzene] allows for fast double coupling of the Grignard reagent with 2,5-dibromothiophene. The concentration of catalyst could be limited to 0.5 mol % based on the amount of 2,5-dibromothiophene. An adapted workup procedure was developed, in which n-octane was used to separate the magnesium salts from the desired product. The reaction was performed in a (semi)batch-wise operated reactor. A global model for the coupling step proved to predict the results at 0.1-, 1-, and 10-L scales very accurately. The heat of reaction evolved in the coupling step was valorized and could be handled easily. Mixing of the feed stream and the reactor content proved to be another important factor in the scaling-up of the α-terthienyl synthesis.
- Smeets,Meijer,Meuldijk,Vekemans,Hulshof
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- Self-assembly and anion encapsulation properties of cavitand-based coordination cages
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Two novel classes of cavitand-based coordination cages 7a-j and 8a-d have been synthesized via self-assembly procedures. The main factors controlling cage self-assembly (CSA) have been identified in (i) a P-M-P angle close to 90° between the chelating ligand and the metal precursor, (ii) Pd and Pt as metal centers, (iii) a weakly coordinated counterion, and (iv) preorganization of the tetradentate cavitand ligand. Calorimetric measurements and dynamic 1H and 19F NMR experiments indicated that CSA is entropy driven. The temperature range of the equilibrium cage-oligomers is determined by the level of preorganization of the cavitand component. The crystal structure of cage 7d revealed the presence of a single triflate anion encapsulated. Guest competition experiments revealed that the encapsulation preference of cages 7b,d follows the order BF4- > CF3SO3- ? PF6- at 300 K. ES-MS experiments coupled to molecular modeling provided a rationale for the observed encapsulation selectivities. The basic selectivity pattern, which follows the solvation enthalpy of the guests, is altered by size and shape of the cavity, allowing the entrance of an ancillary solvent molecule only in the case of BF4-.
- Fochi,Jacopozzi,Wegelius,Rissanen,Cozzini,Marastoni,Fisicaro,Manini,Fokkens,Dalcanale
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p. 7539 - 7552
(2007/10/03)
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- Simultaneous conversion of Ni-PR3 and B-H to Ni-H and B-PR3 linkages by thermal rearrangement of d8 closo-bis(triarylphosphine)nickelacarboranes. Crystal and molecular structure of [closo-3-(μ-CO)-8-PPh3-3,1,2-NiC2B9H 10]2: A dimeric nickelacarborane complex containing a metal-metal bond
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The reaction of L2NiCl2 (L = PR3) species with nido-7,8-, nido-7,9-, or nido-2,9-C2B9H112- ions led to the formation of the corresponding icosahedral bis(phosphine)nickelacarboranes in high yield. Heating members of the closo-3,3-(triarylphosphine)2-3,1,2-NiC2B 9H11 series at 80°C in benzene solution led to the formation of the corresponding [closo-3,8-(triarylphosphine)2-3-H-3,1,2-NiC2B 9H11] by interchange of phosphine and hydrido ligands. No intermediates were observed, and the reaction was specific for the bis(triarylphosphine)-3,1,2-NiC2 icosahedral system among those investigated. The dimeric nickelacarborane carbonyl [closo-(3-(μ-CO)-8-PPh3-3,1,2-NiC2B9H 11)2] was prepared by a variety of routes such as the reaction of [closo-3,3-(PPh3)2-3,1,2-NiC2B 9H11] (1a) with CO in benzene at 80°C. A variety of ligand substitution reactions were carried out with 1a. The mechanism of the phosphine-hydride ligand interchange is discussed. The dimeric nickelacarborane complex was characterized by an X-ray diffraction study. Amber crystals were triclinic, space group P1, with a = 13.319 (4) A?, b = 10.039 (3) A?, c = 9.813 (3) A?, α = 80.00 (1)°, β = 82.91 (1)°, γ = 110.32 (1)°, and Z = 1. The structure was solved by conventional heavy-atom methods to a final discrepancy index of R = 0.057 for 2233 independent observed reflections. The complex contains a metal-metal bond (2.477 (2) A?) and two metal-bridging carbon monoxide groups.
- King III,Miller, Steven B.,Knobler, Carolyn B.,Hawthorne, M. Frederick
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p. 3548 - 3554
(2008/10/08)
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