- A family of rhodium and iridium complexes with semirigid benzylsilyl phosphines: From bidentate to tetradentate coordination modes
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The synthesis of a new trisbenzylsilanephosphine P{(o-C6H4CH2)SiMe2H}3 (1) is shown to proceed with high yields from P(o-tolyl)3. Compound 1 coordinates to the Rh and Ir dimers [MCl(COD)]2 (M = Rh, Ir) in a tetradentate or tridentate fashion, depending on the strict exclusion of water. The dimeric compounds [ClM(SiMe2CH2-o-C6H4)2P(o-C6H4-CH2SiMe2H)]2, 2Rh and 2Ir, feature a tetradentate coordination of the starting ligand with P and two Si atoms as well as a non-classical agostic Si-H group. The presence of adventitious water in the solvents leads to the formation of two new complexes [(μ2-Cl)2M2(SiMe2CH2-o-C6H4)2P(o-C6H4-CH2SiMe2OSiMe2CH2-o-C6H4-)P(SiMe2CH2-o-C6H4)2], 3Rh and 3Ir, which feature a siloxane bridge through Si-H bond breaking in 2. Reaction of [RhCl(COD)]2 with the bisbenzylsilanephosphine PhP{(o-C6H4CH2)SiMe2H}2 leads to the formation of compound 4Rh which features also a dimeric structure with the SiPSi ligand coordinated through the two silicon atoms, one of which occupies the apical position of a square-pyramidal geometry in the solid state, while the second is disposed equatorially trans to π-donor Cl. Finally, bidentate coordination of a PSi ligand is achieved by reaction of [RhCl(COD)]2 with Ph2P{(o-C6H4CH2)SiMe2H} which leads to the monometallic species [RhCl(SiMe2CH2-o-C6H4-PPh2)2], 5Rh, incorporating two chelating PSi ligands and maintaining a Cl ligand.
- Corona-González, María Vicky,Zamora-Moreno, Julio,Cuevas-Chávez, Cynthia A.,Rufino-Felipe, Ernesto,Mothes-Martin, Emmanuelle,Coppel, Yannick,Mu?oz-Hernández, Miguel A.,Vendier, Laure,Flores-Alamo, Marcos,Grellier, Mary,Sabo-Etienne, Sylviane,Montiel-Palma, Virginia
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- Kinetics and Equilibrium of the Reaction between Bis(trifluoroacetylacetonato)palladium(II) and Tri-o-tolylphosphine
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Tri-o-tolylphosphine reacts with bis(trifluoroacetylacetonato)palladium(II), Pd(tfac)2, to convert one of the chelating ligands into the unidentate state, resulting in Pd(tfac)(tfac-O)P(o-tolyl)3.The reaction was studied by a spectrophotometric method.The equilibrium constant was determined at several temperatures, K being 1.38*103, 4.35*103 dm3 mol-1 and more than 109 dm3 mol-1 in benzene, dichloromethane, and methanol, respectively, at 25 deg C.In the presence of excess phosphine, the reaction proceeds as a pseudo first order reaction to attain equilibrium.The forward and reverse rate constants, k1 and k-1, were obtained as 0.172 dm3 mol-1 s-1 and 1.22*10-4 s-1 in benzene and 2.28 dm3 mol-1 s-1 and 4.9*10-4 s-1 in dichloromethane at 25 deg C, respectively.In methanol the forward rate was measured under irreversible pseudo first order conditions and conforms with the usual two term rate law, kobsd/s-1=2*10-3 + 56.6.The remarkable dependence of K and k1 on the nature of solvent is related to the hydrogen bonding interaction between the carbonyl group of the coordinated tfac anion and a solvent molecule.
- Matsumoto, Shinichi,Kawaguchi, Shinichi
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- Photochemical transformation of chlorobenzenes and white phosphorus into arylphosphines and phosphonium salts
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Chlorobenzenes are important starting materials for the preparation of commercially valuable triarylphosphines and tetraarylphosphonium salts, but their use for the direct arylation of elemental phosphorus has been elusive. Here we describe a simple photochemical route toward such products. UV-LED irradiation (365 nm) of chlorobenzenes, white phosphorus (P4) and the organic superphotoreductant tetrakis(dimethylamino)ethylene (TDAE) affords the desired arylphosphorus compounds in a single reaction step.
- Gschwind, Ruth M.,Mende, Michael,Scott, Daniel J.,Streitferdt, Verena,Till, Marion,Wolf, Robert
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supporting information
p. 1100 - 1103
(2022/02/03)
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- A Lewis Base Nucleofugality Parameter, NFB, and Its Application in an Analysis of MIDA-Boronate Hydrolysis Kinetics
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The kinetics of quinuclidine displacement of BH3 from a wide range of Lewis base borane adducts have been measured. Parameterization of these rates has enabled the development of a nucleofugality scale (NFB), shown to quantify and predict the leaving group ability of a range of other Lewis bases. Additivity observed across a number of series R′3-nRnX (X = P, N; R′ = aryl, alkyl) has allowed the formulation of related substituent parameters (nfPB, nfAB), providing a means of calculating NFB values for a range of Lewis bases that extends far beyond those experimentally derived. The utility of the nucleofugality parameter is explored by the correlation of the substituent parameter nfPB with the hydrolyses rates of a series of alkyl and aryl MIDA boronates under neutral conditions. This has allowed the identification of MIDA boronates with heteroatoms proximal to the reacting center, showing unusual kinetic lability or stability to hydrolysis.
- Taylor, Nicholas P.,Gonzalez, Jorge A.,Nichol, Gary S.,García-Domínguez, Andrés,Leach, Andrew G.,Lloyd-Jones, Guy C.
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supporting information
p. 721 - 729
(2022/01/04)
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- Photocatalytic Arylation of P4 and PH3: Reaction Development Through Mechanistic Insight
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Detailed 31P{1H} NMR spectroscopic investigations provide deeper insight into the complex, multi-step mechanisms involved in the recently reported photocatalytic arylation of white phosphorus (P4). Specifically, these studies have identified a number of previously unrecognized side products, which arise from an unexpected non-innocent behavior of the commonly employed terminal reductant Et3N. The different rate of formation of these products explains discrepancies in the performance of the two most effective catalysts, [Ir(dtbbpy)(ppy)2][PF6] (dtbbpy=4,4′-di-tert-butyl-2,2′-bipyridine) and 3DPAFIPN. Inspired by the observation of PH3 as a minor intermediate, we have developed the first catalytic procedure for the arylation of this key industrial compound. Similar to P4 arylation, this method affords valuable triarylphosphines or tetraarylphosphonium salts depending on the steric profile of the aryl substituents.
- Cammarata, Jose,Gschwind, Ruth M.,Lennert, Ulrich,Rothfelder, Robin,Scott, Daniel J.,Streitferdt, Verena,Wolf, Robert,Zeitler, Kirsten
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supporting information
p. 24650 - 24658
(2021/10/14)
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- The Trityl-Cation Mediated Phosphine Oxides Reduction
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Reduction of phosphine oxides into the corresponding phosphines using PhSiH3 as a reducing agent and Ph3C+[B(C6F5)4]? as an initiator is described. The process is highly efficient, reducing a broad range of secondary and tertiary alkyl and arylphosphines, bearing various functional groups in generally good yields. The reaction is believed to proceed through the generation of a silyl cation, which reaction with the phosphine oxide provides a phosphonium salt, further reduced by the silane to afford the desired phosphine along with siloxanes. (Figure presented.).
- Landais, Yannick,Laye, Claire,Lusseau, Jonathan,Robert, Frédéric
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supporting information
p. 3035 - 3043
(2021/05/10)
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- Versatile Visible-Light-Driven Synthesis of Asymmetrical Phosphines and Phosphonium Salts
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Asymmetrically substituted tertiary phosphines and quaternary phosphonium salts are used extensively in applications throughout industry and academia. Despite their significance, classical methods to synthesize such compounds often demand either harsh reaction conditions, prefunctionalization of starting materials, highly sensitive organometallic reagents, or expensive transition-metal catalysts. Mild, practical methods thus remain elusive, despite being of great current interest. Herein, we describe a visible-light-driven method to form these products from secondary and primary phosphines. Using an inexpensive organic photocatalyst and blue-light irradiation, arylphosphines can be both alkylated and arylated using commercially available organohalides. In addition, the same organocatalyst can be used to transform white phosphorus (P4) directly into symmetrical aryl phosphines and phosphonium salts in a single reaction step, which has previously only been possible using precious metal catalysis.
- Arockiam, Percia Beatrice,Lennert, Ulrich,Graf, Christina,Rothfelder, Robin,Scott, Daniel J.,Fischer, Tillmann G.,Zeitler, Kirsten,Wolf, Robert
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supporting information
p. 16374 - 16382
(2020/11/03)
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- Direct and Scalable Electroreduction of Triphenylphosphine Oxide to Triphenylphosphine
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The direct and scalable electroreduction of triphenylphosphine oxide (TPPO)-the stoichiometric byproduct of some of the most common synthetic organic reactions-to triphenylphosphine (TPP) remains an unmet challenge that would dramatically reduce the cost and waste associated with performing desirable reactions that are mediated by TPP on a large scale. This report details an electrochemical methodology for the single-step reduction of TPPO to TPP using an aluminum anode in combination with a supporting electrolyte that continuously regenerates a Lewis acid from the products of anodic oxidation. The resulting Lewis acid activates TPPO for reduction at mild potentials and promotes P-O over P-C bond cleavage to selectively form TPP over other byproducts. Finally, this robust methodology is applied to (i) the reduction of synthetically useful classes of phosphine oxides, (ii) the one-pot recycling of TPPO generated from a Wittig reaction, and (iii) the gram-scale reduction of TPPO at high concentration (1 M) with continuous product extraction and in flow at high current density.
- Manabe, Shuhei,Sevov, Christo S.,Wong, Curt M.
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p. 3024 - 3031
(2020/03/10)
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- Substituent steric effect boosting phosphorescence efficiency of PtCu2 complexes
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We describe herein a viable approach to enhance phosphorescence efficiency in PtCu2 complexes with aromatic acetylides by the use of bis(di-2-tolylphosphinomethyl)phenylphosphine (dTolmp) in place of bis(diphenylphosphinomethyl)-phenylphosphine (dpmp) as a supporting ligand. Relative to dpmp-supported PtCu2 complexes, dTolmp-supported complexes having the same acetylide ligands show not only a 16-36 nm red-shift of the emission peaks, but also a dramatic phosphorescence enhancement. The phosphorescence quantum yields of dTolmp-supported PtCu2 complexes are boosted to 6.6 and 11.6 times as high as those of the dpmp-supported ones in CH2Cl2 solutions and the solid state, respectively. From dpmp to dTolmp, introducing sterically hindered 2-methyl groups to phenyl rings not only improves the π-conjugation character of PtCu2 complexes, but also effectively inhibits the deactivation process of the triplet excited state through non-radiative relaxation. The phosphorescence properties were systematically modulated in a wide spectral range from 502 to 672 nm by introducing electron-donating or electron-withdrawing substituents into aromatic acetylides.
- Chen, Zhong-Ning,Wang, Jin-Yun,Wang, Zhao-Yi,Yang, Ming,Zhang, Li-Yi,Zhang, Xu
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supporting information
p. 5174 - 5182
(2020/04/28)
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- Superbase-Assisted Selective Synthesis of Triarylphosphines from Aryl Halides and Red Phosphorus: Three Consecutive Different SNAr Reactions in One Pot
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Aryl halides, ArX (Ar = Ph, 2-, 3- and 4-Tol, 1- and 2-Np, 4-C6H4CONH2; X = F, Cl, Br), rapidly and exothermically (100–180 °C, 0.5–2 h) react with red phosphorus in superbase systems KOH/L, where L is a polar nonhydroxylic complexing solvent (ligand), such as NMP, DMSO, HMPA, to afford the corresponding triarylphosphines (Ar3P) in up to 74 % yield (for X = F). Thus, three consecutive reactions of SNAr (aromatic nucleophilic substitution) to form the three C(sp2)–P bonds are realized in one pot. The synthesis is mostly chemoselective (with rare exception): neither mono- nor diphosphines have been isolated. The best results were attained when aryl fluorides were treated with red phosphorus (Pn) in the KOH/NMP superbase system. This environmentally friendly, PCl3-free synthesis of Ar3P from available starting materials opens an easy and straightforward access to triarylphosphines, which are important ligands, synthetic auxiliaries, and components of high-tech- and medicinally oriented complexes.
- Malysheva, Svetlana F.,Kuimov, Vladimir A.,Belogorlova, Natalia A.,Albanov, Alexander I.,Gusarova, Nina K.,Trofimov, Boris A.
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supporting information
p. 6240 - 6245
(2019/11/05)
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- Electrophilic Phosphonium Cation-Mediated Phosphane Oxide Reduction Using Oxalyl Chloride and Hydrogen
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The metal-free reduction of phosphane oxides with molecular hydrogen (H2) using oxalyl chloride as activating agent was achieved. Quantum-mechanical investigations support the heterolytic splitting of H2 by the in situ formed electrophilic phosphonium cation (EPC) and phosphane oxide and subsequent barrierless conversion to the phosphane and HCl. The reaction can also be catalyzed by the frustrated Lewis pair (FLP) consisting of B(2,6-F2C6H3)3 and 2,6-lutidine or phosphane oxide as Lewis base. This novel reduction was demonstrated for triaryl and diaryl phosphane oxides providing access to phosphanes in good to excellent yields (51–93 %).
- Stepen, Arne J.,Bursch, Markus,Grimme, Stefan,Stephan, Douglas W.,Paradies, Jan
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supporting information
p. 15253 - 15256
(2018/10/24)
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- Mechanistic Investigations of Reactions of the Frustrated Lewis Pairs (Triarylphosphines/B(C6F5)3) with Michael Acceptors
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Frustrated Lewis pair (FLP)-catalyzed reduction of Michael acceptors is a challenging reaction that proceeds with specific FLP structures. Kinetics and equilibrium of the reactions of two phosphines (Ar3P), namely tri(1-naphthyl)phosphine and tri(o-tolyl)phosphine, are reported with reference electrophiles. The reason for the failure of the FLPs (Ar3P/B(C6F5)3) to reduce activated alkenes under H2 pressure is shown to be a hydrophosphination process that inhibits the reduction reaction. Kinetic and thermodynamic factors controlling both pathways are discussed in light of Mayr's free linear energy relationships.
- Dupré, Jonathan,Gaumont, Annie-Claude,Lakhdar, Sami
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supporting information
p. 694 - 697
(2017/02/10)
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- Reactivity of dimeric cyclopalladated complexes with an (sp3)C-Pd bond toward KPPh2
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Abstract Reactions of KPPh2 with dimeric C,N, C,P and C,S cyclopalladated complexes (CPCs) 1a-g containing an (sp3)C-Pd bond were investigated. The CPCs used in the study were obtained from D-camphor O-methyloxime (a), l-fenchone O-methyloxime (b), 4,4-dimethyl-2-phenyl-2-oxazoline (c), 8-methylquinoline (d), trimesitylphosphine (e), tri(O-tolyl)phosphine (f) and 2,6-dimethylthioanisole (g). The dichloro-bridged CPCs 1a,b,d,f,g and the diacetato-bridged analog μ-OAc-1d reacted with 4.5 equiv. of KPPh2 at room temperature in THF to give either phosphines 2a,b or phosphine oxides 8d,f,g in 20-51% yield. Complexes 1a,b,d reacted with 1 equiv. of KPPh2 to produce the corresponding μ-chloro-μ-diphenylphosphido-CPCs 3a,b,d in 33-56% yield. In the reaction of CPC 1c with 4.5 equiv. of KPPh2, complex 4c with two PPh2 bridging ligands was isolated in 36% yield. Structures of phosphines 2a,b, phosphine oxides 8a,d,f,g as well as complexes 3a,b,d and 4c were confirmed by 1H, 13C{1H} and 31P{1H} NMR spectroscopy.
- Dickmu, Gerard C.,Korte, Nicholas J.,Smoliakova, Irina P.
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- Reduction of phosphine oxides to the corresponding phosphine derivatives in Mg/Me3SiCl/DMI system
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Direct reductions of phosphine oxides to the corresponding phosphines were performed successfully by using Mg/Me3SiCl/DMI system. The reduction proceeded under mild conditions and was applicable to a wide range of phosphine oxides; triarylphosphine oxides, alkyldiarylphosphine oxides, and dialkylarylphosphine oxides gave the corresponding phosphines in good to excellent yields.
- Kuroboshi, Manabu,Kita, Toshihito,Aono, Asuka,Katagiri, Toshimasa,Kikuchi, Seiya,Yamane, Syoko,Kawakubo, Hiromu,Tanaka, Hideo
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p. 918 - 920
(2015/02/05)
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- Silylium ion/phosphane lewis pairs
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The reactivity of a series of silylium ion/phosphane Lewis pairs was studied. Triarylsilylium borates 4[B(C6F5)4] form frustrated Lewis pairs (FLPs) of moderate stability with sterically hindered phosphanes 2. Some of these FLPs are able to cleave dihydrogen under ambient conditions. The combination of bulky trialkylphosphanes with triarylsilylium ions can be used to sequester CO2 in the form of silylacylphosphonium ions 12. The ability to activate molecular hydrogen by reaction of silylium ion/phosphane Lewis pairs is dominated by thermodynamic and steric factors. For a given silylium ion increasing proton affinity and increasing steric hindrance of the phosphane proved to be beneficial. Nevertheless, excessive steric hindrance leads to a breakdown of the dihydrogen-splitting activity of a silylium/phosphane Lewis pair.
- Reissmann, Matti,Schaefer, Andre,Jung, Sebastian,Mueller, Thomas
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p. 6736 - 6744
(2014/01/06)
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- Electroreduction of triphenylphosphine oxide to triphenylphosphine in the presence of chlorotrimethylsilane
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Electroreduction of triphenylphosphine oxide to triphenylphosphine in an acetonitrile solution of tetrabutylammonium bromide in the presence of chlorotrimethylsilane was performed successfully in an undivided cell fitted with a zinc anode and a platinum cathode under constant current. A plausible mechanism involving, (1) one-electron reduction of triphenylphosphine oxide generating the corresponding anion radical [Ph3P-O-], (2) subsequent reaction with chlorotrimethylsilane affording the (trimethylsiloxy)triphenylphosphorus radical [Ph3P-OSiMe 3], and (3) further one-electron reduction followed by P-O bond fission leading to triphenylphosphine is proposed. In a similar manner, electroreduction of some triarylphosphine oxides and alkyldiarylphosphine oxides was executed to give the corresponding phosphine derivatives in good to moderate yields. Georg Thieme Verlag Stuttgart · New York.
- Kawakubo, Hiromu,Kuroboshi, Manabu,Yano, Tomotake,Kobayashi, Kazuma,Kamenoue, Syogo,Akagi, Tomomi,Tanaka, Hideo
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scheme or table
p. 4091 - 4098
(2012/01/12)
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- PROCESS FOR PRODUCTION OF PHOSPHINE DERIVATIVE FROM PHOSPHINE OXIDE DERIVATIVE
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Disclosed is a process for producing a phosphine derivative from a phosphine oxide derivative, which comprises the following steps: (I) mixing a phosphine oxide derivative represented by formula (1) with a chlorinating agent in a polar organic solvent to cause the reaction between these components; and (II-1) adding a salt of a metal having an ionization tendency equal to or lower than that of aluminum to the reaction mixture and carrying out the reductive reaction in the presence of aluminum or (II-2) subjecting the reaction mixture to electrolytic reduction, thereby producing a phosphine derivative represented by formula (2). ArnR3-nP═O (1) ArnR3-nP (2) In formulae (1) and (2), Ar represents an aryl group such as a phenyl group, a phenyl group having a substituent, a heteroaromatic ring group, and a heteroaromatic ring group having a substituent; R represents an aliphatic hydrocarbon group or an aliphatic hydrocarbon group having a substituent; and n represents an integer of 0 to 3.
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Page/Page column 10
(2011/04/18)
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- Dihydrogen activation by B(p-C6F4H)3 and phosphines
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The Grignard reagent (p-C6F4H)MgCl was used to prepare (Et2O)B(p-C6F4H)3 (2) and the free borane B(p-C6F4H)3 (1). On the basis of Lewis acidity tests, the borane 1 exhibits ca. 95% of the acidity of B(C 6F5)3. 1 forms classical adducts with ethers and phosphines of the general formula (L)B(p-C6F4H) 3 (L = Et2O (2), THF (3), Me3P (4), Et 3P (5), i-Pr2(H)P (6), Ph3P (7), (3,5-Me 2C6H3)3P (8), t-Bu2(H)P (9), and Cy3P (10)). Compounds 9 and 10 react with 4 atm of H 2 to give the salts [t-Bu2PH2][HB(p-C 6F4H)3] (11) and [Cy3PH][HB(p-C 6F4H)3] (12). The sterically demanding phosphines R3P (R = t-Bu, i-Pr, 2,4,6-Me3C 6H2, and 2-MeC6H4), R 2R′P (R,R′ = t-Bu, i-Pr and t-Bu, Cy), and (Ph 2CH)R2P (R = t-Bu (22), i-Pr (23), Cy (24), and C 5H9 (25)) show no evidence of adduct formation with 1, but react with H2 to give the corresponding salts [R3PH] [HB(p-C6F4H)3] (13-16), [R2R′ PH][HB(p-C6F4H)3] (17-20), and [(Ph 2CH)R2PH][HB(p-C6F4H)3] (26-29), respectively. The [t-Bu2PH2]+ species 11 is stable only under an H2 overpressure, while the [t-Bu 3PH]+ salt 13 cleanly extrudes isobutene and H2 at elevated temperatures to give 9. The [(2-MeC6H4) 3PH]+ derivative 16 readily liberates H2 under vacuum, thus providing a metal-free system capable of reversible H2 uptake and release. Crystallographic data for compounds 1, 5, 8, 9, 10, 13, and 26 are reported.
- Ullrich, Matthias,Lough, Alan J.,Stephan, Douglas W.
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p. 3647 - 3654
(2010/10/04)
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- Catalyst-free alcoholysis of phosphane-boranes: a smooth, cheap, and efficient deprotection procedure
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Catalyst-free alcoholytic deprotection of borane-protected phosphorus compounds offers a smooth, efficient, and clean alternative to existing deprotection methods. In this paper we report our results on the general applicability of deprotecting phosphane-
- Van Overschelde, Michel,Vervecken, Elias,Modha, Sachin G.,Cogen, Simon,Van der Eycken, Erik,Van der Eycken, Johan
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experimental part
p. 6410 - 6415
(2009/12/09)
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- Process for the preparation of epsilon-Caprolactam
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The invention relates to a process for the preparation of ε-caprolactam, wherein ε-caprolactam is prepared starting from butadiene, carbon monoxide, hydrogen and ammonia and the process comprises:1. carbonylating butadiene in the presence of an alkanol and a catalyst comprising palladium, a multidentate phosphine ligand and an acidic co-catalyst to produce alkyl-4-, alkyl-3- and alkyl-2-pentenoate,1'. optionally isomerising the alkyl-3- and/or alkyl-2-pentenoate into alkyl-4-pentenoate,2. hydroformylating the alkyl-4-, alkyl-3- and alkyl-2-pentenoate in the presence of a catalyst comprising rhodium and an organic phosphorous containing ligand to produce alkyl-5-formylvalerate,3. reductively aminating alkyl-5-formylvalerate in the presence of a hydrogenation catalyst comprising ruthenium on a carrier catalyst to produce ε-caprolactam and ε-caprolactam precursors,4. optionally converting ε-caprolactam precursors at elevated temperature into ε-caprolactam.
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- Process for the continuous preparation of alkyl 5-formylvalerate compounds using homogeneous rhodium hydroformylation catalysts
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Process for the continuous preparation of an alkyl 5-formylvalerate by reacting an alkyl-3-pentenoate with carbon monoxide and hydrogen by hydroformylation using a catalyst system comprising rhodium or iridium and a multidentate organic phosphite ligand according to the general formula: in which n is 2-6, X is an n-valent organic bridging group, and in which the end groups R1-R2are monovalent aryl groups, wherein the process is carried out in the presence of an acid compound having a pKa between 1 and 12 measured in water at 18° C.
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- Sulfonated phosphines, processes for their preparation, and use thereof as constituents of catalyst systems
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Sulfonated phosphines of the formula STR1 in which R is cyclohexyl or alkyl having 1 to 4 carbon atoms, M is hydrogen, alkyl substituted ammonium, aryl substituted-ammonium, monovalent metal, or the chemical equivalent of a polyvalent metal, x is 1, 2, or 3 and n is 0 or 1. These compounds are obtained by sulfonation of the non-sulfonated parent substances with oleum or an anhydrous mixture of sulfuric acid and orthoboric acid.
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- The basicity of phosphines
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The basicities of the triarylphosphines P(4-XC6H4)3 (X = Cl, F, H, CH3, CH3O, (CH3)2N), P(3-CH3C6H4)3, and P(2-CH3C6H7)3 as well as the trialkylphosphines P(t-Bu)3 and PCy3 have been measured by the nitromethane titration method.The range of basicity available by aryl substitution is very large, being pKa = 8. 65 for X = (CH3)2N to 1.03 for X = Cl.The most basic phosphine is P(t-Bu)3 whose pKa = 11.40.The measured basicities correlate well wit ?p, ?Φ, and ν as well as with the lone pair ionisation potentials of the triarylphosphines.Generally the 1H,31P, and 13C nmr spectral parameters of the free and protonated phosphines do not correlate well with pKa.
- Allman, Tim,Goel, Ram G.
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p. 716 - 722
(2007/10/02)
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