- Synthesis and Reactivity of Palladium(II) Alkyl Complexes that Contain Phosphine-cyclopentanesulfonate Ligands
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The synthesis of the phosphine-cyclopentanesulfonate pro-ligands Li/K[2-PPh2-cyclopentanesulfonate] (Li/K[2a]), Li/K[2-P(2-OMe-Ph)2-cyclopentanesulfonate] (Li/K[2b]), and H[2b], and the corresponding Pd(II) alkyl complexes (κ2-P,O-2a)PdMe(pyridine) (3a) and (κ2-P,O-2b)PdMe(pyridine) (3b) is described. The sulfonate-bridged base-free dimer {(2b)PdMe}2 (4b) was synthesized by abstraction of pyridine from 3b using B(C6F5)3. The borane-coordinated base-free dimer [{2b·B(C6F5)3}PdMe]2 (5b), in which B(C6F5)3 binds to a sulfonate oxygen, was prepared by addition of 1 equiv of B(C6F5)3 per Pd to 4b or addition of 2 equiv of B(C6F5)3 to 3b. Compounds 3b, 4b, and 5b polymerize ethylene with low activity (up to 210 kg mol-1 h-1 at 250 psi and 80 °C) to linear polyethylene (Mn = 1950-5250 Da) with predominantly internal olefin placements. 3b and 4b copolymerize ethylene with methyl acrylate to linear copolymers that contain up to 11.7 mol % methyl acrylate, which is incorporated as -CH2CH(CO2Me)CH2- (80%) in-chain units and -CH2CH(CO2Me)Me (8%) and -CH2CH-CH(CO2Me) (12%) chain-end units. 3b and 4b also copolymerize ethylene with vinyl fluoride to linear copolymers that contain up to 0.41 mol % vinyl fluoride, which is incorporated as -CH2CHFCH2- (~80%) in-chain units and -CH2CF2H (7%), -CH2CHFCH3 (5%), and -CH2CH2F (8%) chain-end units. Complexes 3b and 4b are more stable and active in ethylene polymerization than analogous (PAr2-CH2CH2SO3)PdR catalysts, but are less active than analogous (PAr2-arenesulfonate)PdR catalysts. Low-temperature NMR studies show that 4b reacts with ethylene below -10 °C to form the ethylene adduct cis-P,R-(2b)PdMe(ethylene) (7b), which undergoes ethylene insertion at 5 °C. DFT calculations for a model (PMe2-cyclopentanesulfonate)Pd(Pr)(ethylene) species show that ethylene insertion proceeds by cis-P,R/trans-P,R isomerization followed by migratory insertion, and that the lower activity of 3b and 4b vis-à-vis analogous (PAr2-arenesulfonate)PdR catalysts results from a higher barrier for migratory insertion of the trans-P,R isomer.
- Black, Rebecca E.,Jordan, Richard F.
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- Rigidifying Cation-Tunable Nickel Catalysts Increases Activity and Polar Monomer Incorporation in Ethylene and Methyl Acrylate Copolymerization
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In this study, we synthesized and characterized two nickel complexes featuring conformationally rigid bisphosphine mono-oxide ligands, where one has an o-methoxyphenyl (Ni2) and the other has an o-(2-methoxyethoxy)phenyl (Ni3) substituent on the Pa? O moiety. We performed metal binding studies using Ni3 and found that its reaction with Li+ and Na+ most likely produced 1:1 and 1:1/2:1 nickel:alkali species in solution, respectively. The nickel complexes were competent catalysts for ethylene homopolymerization and copolymerization, with activities up to 3.8 × 103 and 8.1 × 10 kg mol-1 h-1, respectively. In reactions of ethylene with methyl acrylate (1.0 M), the addition of Li+ to Ni3 led to a 5.4-fold enhancement in catalyst activity and a 1.9-fold increase in polar monomer incorporation in comparison to those by Ni3 alone under optimized conditions. A comparison with other nickel catalysts reported for ethylene and methyl acrylate copolymerization revealed that our nickel-alkali catalysts are competitive with some of the most efficient Ni-based systems developed thus far.
- Tahmouresilerd, Babak,Xiao, Dawei,Do, Loi H.
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supporting information
p. 19035 - 19043
(2021/12/13)
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- Method for synthesizing bis(2-methoxyphenyl) phosphine oxide
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The invention belongs to the technical field of fine chemical industry, and particularly relates to a method for synthesizing bis(2-methoxyphenyl) phosphine oxide. The method comprises the following steps: a) carrying out a reaction of anisole and triethyl phosphate in a solvent to obtain ethyl bis(2-methoxyphenyl)phosphonate; and b) performing hydrogenation reduction on ethyl bis(2-methoxyphenyl)phosphonate in a solvent to obtain bis(2-methoxyphenyl) phosphine oxide. The method uses anisole as a starting raw material, first the reaction of anisole and triethyl phosphate is carried out to obtain ethyl bis(2-methoxyphenyl)phosphonate, and then hydrogenation reduction is carried out to synthesize bis(2-methoxyphenyl) phosphine oxide. The method has simple reaction, high conversion rate, andexcellent product quality. The content of bis(2-methoxyphenyl) phosphine oxide produced by the method is 98% or more, technical requirements for producing related polyketone ligands in the market aremet, the operation steps are simple, required equipment is simple, and energy consumption is low.
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Paragraph 0025; 0046-0052; 0054-0059; 0060-0065; 0066-0071
(2020/01/03)
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- Preparation of O-Protected Cyanohydrins by Aerobic Oxidation of α-Substituted Malononitriles in the Presence of Diarylphosphine Oxides
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A mild, reagent-cyanide-free, and efficient synthesis of O-phosphinoyl-protected cyanohydrins from readily available α-substituted malononitriles was realized using diarylphosphine oxides in the presence of O2. Mechanistic studies indicated that in addition to the initial aerobic oxidation of the malononitrile derivative notable features of this process include the formation of a tetrahedral intermediate and a subsequent intramolecular rearrangement. The phosphinoyl-protecting group can be removed by alcoholysis or by reduction with DIBAL-H.
- Zhang, Dapeng,Lian, Mingming,Liu, Jia,Tang, Shukun,Liu, Guangzhi,Ma, Cunfei,Meng, Qingwei,Peng, Haisheng,Zhu, Daling
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supporting information
p. 2597 - 2601
(2019/04/17)
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- Rapid Metal-Free Formation of Free Phosphines from Phosphine Oxides
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A rapid method for the reduction of secondary phosphine oxides under mild conditions has been developed, allowing simple isolation of the corresponding free phosphines. The methodology involves the use of pinacol borane (HBpin) to effect the reduction while circumventing the formation of a phosphine borane adduct, as is usually the case with various other commonly used borane reducing agents such as borane tetrahydrofuran complex (BH3?THF) and borane dimethyl sulfide complex (BH3?SMe2). In addition, this methodology requires only a small excess of reducing agent and therefore compares favourably not just with other borane reductants that do not require a metal co-catalyst, but also with silane and aluminium based reagents. (Figure presented.).
- Provis-Evans, Cei B.,Emanuelsson, Emma A. C.,Webster, Ruth L.
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supporting information
p. 3999 - 4004
(2018/09/21)
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- Selective dehydrocoupling of phosphines by lithium chloride carbenoids
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The development of a simple, transition-metal-free approach for the formation of phosphorus-phosphorus bonds through dehydrocoupling of phosphines is presented. The reaction is mediated by electronically stabilized lithium chloride carbenoids and affords a variety of different diphosphines under mild reaction conditions. The developed protocol is simple and highly efficient and allows the isolation of novel functionalized diphosphines in high yields.
- Molitor, Sebastian,Becker, Julia,Gessner, Viktoria H.
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supporting information
p. 15517 - 15520
(2014/12/12)
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- On Ni catalysts for catalytic, asymmetric Ni/Cr-mediated coupling reactions
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The importance of the Ni catalyst in achieving catalytic asymmetric Ni/Cr-mediated coupling reactions effectively is demonstrated. Six phenanthroline-NiCl2 complexes 1a-c and 2a-c and five types of alkenyl iodides A-E were chosen for the study, thereby demonstrating that these Ni catalysts display a wide range of overall reactivity profiles in terms of the degree of asymmetric induction, geometrical isomerization, and coupling rate. For three types of alkenyl iodides A-C, a satisfactory Ni catalyst(s) was found within 1a-c and 2a-c. For disubstituted (Z)-alkenyl iodide D, 2c was identified as an acceptable Ni catalyst in terms of the absence of Z → E isomerization and the degree of asymmetric induction but not in terms of the coupling rate. Two phosphine-based Ni catalysts, [(Me)3P]2· NiCl2 and [(cy)3P]2·NiCl2, were found to meet all three criteria for D. The bond-forming reaction at the C16-C17 position of palytoxin was used to demonstrate the usefulness of the Ni catalysts thus identified.
- Liu, Xiang,Li, Xiaoyong,Chen, Yu,Hu, Yimin,Kishi, Yoshito
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supporting information; scheme or table
p. 6136 - 6139
(2012/05/07)
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- A superior method for the reduction of secondary phosphine oxides
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(Chemical Equation Presented) Diisobutylaluminum hydride (DIBAL-H) and triisobutylaluminum have been found to be outstanding reductants for secondary phosphine oxides (SPOs). All classes of SPOs can be readily reduced, including diaryl, arylalkyl, and dialkyl members. Many SPOs can now be reduced at cryogenic temperatures, and conditions for preservation of reducible functional groups have been found. Even the most electron-rich and sterically hindered phosphine oxides can be reduced in a few hours at 50-70°C. This new reduction has distinct advantages over existing technologies.
- Busacca, Carl A.,Lorenz, Jon C.,Grinberg, Nelu,Haddad, Nizar,Hrapchak, Matt,Latli, Bachir,Lee, Heewon,Sabila, Paul,Saha, Anjan,Sarvestani, Max,Shen, Sherry,Varsolona, Richard,Wei, Xudong,Senanayake, Chris H.
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p. 4277 - 4280
(2007/10/03)
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- A new performance of the reaction of PCl3/AlCl3 with anisoles - One-pot and multi-step syntheses of a new fused-ring system [1,2,3]benzoxadiphospholo[2,3-b][1,2,3]benzoxadiphosphole
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Anisoles 4 react with AlCl3 and PCl3 to yield the new fused bicyclic system derivatives 5 and 6 as major products in a one-pot procedure. An alternative multi-step synthesis of this system is also reported in which bis(o-methoxyaryl)phosphane oxides 11 are treated with AlCl3 and PCl3; the diarylphosphane oxides 11 are obtained by a new simple method.
- Baccolini, Graziano,Bazzocchi, Michele,Boga, Carla
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p. 2229 - 2233
(2007/10/03)
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