- 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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Read Online
- An Interrupted Pummerer/Nickel-Catalysed Cross-Coupling Sequence
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An interrupted Pummerer/nickel-catalysed cross-coupling strategy has been developed and used in the elaboration of styrenes. The operationally simple method can be carried out as a one-pot process, involves the direct formation of stable alkenyl sulfonium salt intermediates, utilises a commercially available sulfoxide, catalyst, and ligand, operates at ambient temperature, accommodates sp-, sp2-, and sp3-hybridised organozinc coupling partners, and delivers functionalised styrene products in high yields over two steps. An interrupted Pummerer/cyclisation approach has also been used to access carbo- and heterocyclic alkenyl sulfonium salts for cross-coupling.
- Aukland, Miles H.,Talbot, Fabien J. T.,Fernández-Salas, José A.,Ball, Matthew,Pulis, Alexander P.,Procter, David J.
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supporting information
p. 9785 - 9789
(2018/07/31)
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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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- Stoichiometric reduction of CO2 to CO by phosphine/AlX 3-based frustrated Lewis pairs
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The reactions of the bulky phosphines Mes3P or (otol) 3P with AlX3 (X = I, Br, Cl) and CO2 are probed and shown to give complexes of the form Mes3PC(OAlX 3)2 (X = I (3), Br (4), Cl (5)) and (otol) 3PC(OAlI3)2 (6). The former compounds under CO2 are further transformed to Mes3PC(OAlX 2)2OAlX3 (X = I (8), Br (10)) and [Mes 3PX][AlX4] (X = I (9), Br (11)). These latter reactions are thought to proceed via dissociation of alane, as evidenced by the generation of (otol)3PC(OAl(C6F5)3) from (otol)3PC(OAl(C6F5)3)2 (7) and the isolation of (otol)3PC(O)OAl(OC(CF3) 3)3 (15). Subsequent insertion of CO2 into the Al-X bond is evidenced by the characterization of [(C6F 5)C(O)OAl(C6F5)2]2 (14) from the reaction of Al(C6F5)3 and CO 2. The isolation of Al(C6F5) 3·2(C6H5Br) (16) also suggests dissociation of Al(C6F5)3 from 7 may be facilitated by interactions with solvent. Kinetics of the formation of 8/9 from 3 show the reaction is first order in 3 and CO2 and the rate-determining step involves an associative process. A mechanism involving dissociation of alane and subsequent insertion of CO2 into the Al-X bond is proposed.
- Menard, Gabriel,Gilbert, Thomas M.,Hatnean, Jillian A.,Kraft, Anne,Krossing, Ingo,Stephan, Douglas W.
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supporting information
p. 4416 - 4422
(2013/09/02)
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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 11; 12
(2011/04/18)
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- A new synthesis of triarylsilylium ions and their application in dihydrogen activation
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Well-shuffled: An unexpected substituent distribution reaction via alkyldiarylsilylium ions leads to a distribution of substituents. Starting from alkyldiaryl silanes, this reaction provides a facile synthetic approach to sterically highly hindered triarylsilylium ions. These silylium ions can be applied in dihydrogen activation reactions. Copyright
- Schaefer, Andre,Reissmann, Matti,Schaefer, Annemarie,Saak, Wolfgang,Haase, Detlev,Mueller, Thomas
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supporting information; experimental part
p. 12636 - 12638
(2012/02/15)
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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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- Effects of substituents on aryl groups during the reaction of triarylphosphine radical cation and oxygen
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In a previous report (S. Yasui, S. Tojo and T. Majima, J. Org. Chem., 2005, 70, 1276), we presented the results from the laser flash photolysis (LFP) and product analysis of the 9,10-dicyanoanthracene (DCA)-photosensitized oxidation of triarylphosphine (Ar3P) in acetonitrile under air, which showed that the photoreaction results in the oxidation of Ar3P to give the corresponding phosphine oxide (Ar3PO) in a nearly quantitative yield, and that the reaction is initiated by the electron transfer (ET) from Ar 3P to DCA in the singlet excited state (1DCA*), producing the triarylphosphine radical cation Ar3P+. This radical cation decays through radical coupling with O2 to afford the peroxy radical cation Ar3P+-O-O, which we proposed to be the intermediate leading to the product Ar3PO. We now examined this photoreaction in more detail using ten kinds of Ar3P with various electronic and steric characteristics. The decay rate of Ar3P + measured by the LFP was only slightly affected by the substituents on the aryl groups of Ar3P. During the photolysis of trimesitylphosphine (Mes3P), the peroxy radical cation intermediate (Mes3P+-O-O) had a lifetime long enough to be spectrophotometrically detected. The quantum yields of Ar3PO increased with either electron-withdrawing or -releasing substituents on the aryl groups, suggesting that a radical center is developed on the phosphorus atom during the step when the quantum yield is determined. In addition, the o-methyl substituents in Ar3P decreased the quantum yield. These results clearly indicated that Ar3P+-O-O undergoes radical attack upon the parent phosphine Ar3P that eventually produces the final product, Ar3PO. The Royal Society of Chemistry 2006.
- Yasui, Shinro,Tojo, Sachiko,Majima, Tetsuro
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p. 2969 - 2973
(2008/02/11)
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- Syntitesis and redox properties of sterically hindered meta- and para-Aminophosphinobenzenes
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Meta- and para- aminophosphinobenzenes composed of para substituted triarylamine and all ortho methylated triarylphosphine moieties were synthesized and their redox properties were investigated by cyclic voltammetry.
- Sasaki, Shigeru,Murakami, Fumiki,Yoshifuji, Masaaki
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p. 7095 - 7098
(2007/10/03)
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- The Synthesis and Structural Characterization of Mesityldiphenylphosphine, Dimesitylphenylphosphine and Trimesitylphosphine
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The synthesis and structural characterization of the tertiary phosphines mesityldiphenylphosphine , dimesitylphenylphosphine and a new phase of trimesitylphosphine have been carried out.Crystals of PPh2(mes) are monoclinic, space group P21/c, with a 10.252(10), b 9.847(11), c 17.444(7) Angstroem, β 99.78(6) deg, Z 4; R 0.059 for 2102 "observed" reflections.Crystals of PPh(mes)2 are also monoclinic, space group P21/c, with a 8.964(9), b 22.99(1), c 10.228(4) Angstroem, β 107.98(5) deg, Z 4; R 0.058 for 2350 "observed" reflections.The new phase of P(mes)3 is monoclinic, Cc, a 11.390(5), b 12.034(4), c 17.564(9) Angstroem, β 104.22(4) deg, Z 4 (R 0.060 for 1046 "observed" reflections), in which the molecule is disordered.A full report is given for the phase previously studied (triclinic), P, a 8.191(3), b 16.447(5), c 18.667(6) Angstroem, α 104.82(3), β 97.74(3), γ 100.07(3) deg, Z 4; R 0.065 for 4964 "observed" reflections.The P-C bond distances are similar for the whole series of compounds with an average value of 1.833(1) Angstroem.Introduction of the mesityl groups results in an increase of the C-P-C angles from c. 103 to c. 110 deg with a concomitant flattening of the PC3 pyramid.
- Blount, John F.,Camp, David,Hart, Robert D.,Healy, Peter C.,Skelton, Brian W.,White, Allan H.
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p. 1631 - 1640
(2007/10/02)
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- Rearrangements of the Methyltrimesitylphosphonium and Methylenebis(methyldimesitylphosphonium) Cation Skeletons on Treatment with Base
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The treatment of methyltrimesitylphosphonium iodide (1) with sodium amide or butyllithium leads neither to the corresponding phosphorus ylide nor to the product of a Stevens rearrangement, but affords instead methylmesitylphosphane (4).The product, which is probably formed via a mesityl migration in an 2-methylenecyclohexadienylidenephosphorane intermediate (2b), is structurally characterized by detailed NMR analysis and through hydrochloride and methoiodide derivatives. - Analogous treatment of methylenebis(methyldimesitylphosphonium iodide) (10) with base leads to a pair of diastereomeric cyclic carbodiphosphoranes (12a, b), with elimination of mesitylene.The two carbodiphosphoranes are converted into the diastereomeric diphosphonium salts 13a, b with HCl.The ring closure leading to carbodiphosphorane formation is again interpreted in terms of an intramolecular process involving an 2-methylenecyclohexadienylidene intermediate.Deprotonation of the methylenebis(methyldi-o-tolylphosphonium) cation yields the corresponding carbodiphosphorane 18 without changes in the skeleton.
- Schmidbaur, Hubert,Schnatterer, Stefan
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p. 1947 - 1954
(2007/10/02)
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