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Berthold Hoge - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Unsymmetrically Substituted Phosphane Oxides ((RRP)-R-1-P-2(O)H) and Phosphinous Acids ((RRPOH)-R-1-P-2)
Chemistry: A European Journal, 2020Co-Authors: Nadine Allefeld, Nikolai Ignat'ev, Michael Grasse, Berthold HogeAbstract:This paper describes the synthesis of unsymmetrically substituted Phosphinous Acids and phosphane oxides featuring at least one electron-withdrawing pentafluoroethyl group. The presence of a diethylamino function as a protecting group allows a selective reaction of RClPNEt2 (R=CF3, C6F5, C6H5) with LiC2F5. On treatment with para-toluenesulfonic Acid the isolated aminophosphanes R(C2F5)PNEt2 are readily converted into the corresponding Phosphinous Acids or phosphane oxides, respectively. Investigation of the tautomeric equilibrium between oxide and Acid tautomer revealed (CF3)(C2F5)POH as a stable Phosphinous Acid, whereas the pentafluorophenyl and phenyl derivatives constitute a solvent dependent equilibrium between the Acid and the oxide tautomer.
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Transition Metal Complexes of Phosphinous Acids Featuring a Quasichelating Unit: Synthesis, Characterization, and Hetero-bimetallic Complexes.
Inorganic Chemistry, 2015Co-Authors: Nadine Allefeld, Julia Bader, Beate Neumann, Hans-georg Stammler, Nikolai Ignat'ev, Berthold HogeAbstract:Diorganophosphane oxides were employed as preligands for the synthesis of catalytically active transition metal complexes of the Phosphinous Acids (CF3)2POH and (C2F5)2POH. Their reactions with solid PtCl2 and PdCl2 led to the formation of mononuclear Phosphinous Acid complexes [Cl2M{P(Rf)2OH}2] (M = Pd, Pt; Rf = C2F5, CF3), which can be crystallized, for example, as its pyridinium salts, 2[HPy]+[Cl2Pd{P(CF3)2O}2]2–. In vacuo HCl is liberated from the neutral palladium complexes affording mixtures of di- and polynuclear complexes. Moreover, (C2F5)2POH was reacted with several β-diketonato complexes of palladium, platinum, and nickel yielding air- and moisture-stable complexes [(acac)M{[P(Rf)2O]2H}], featuring a quasichelating Phosphinous Acid phosphinito unit {P(Rf)2O···H···O(Rf)2P}−. Treatment of [Ni(Cp)2] (Cp = cyclopentadienyl) and [(cod)RhCl]2 (cod = 1,5-cyclooctadiene) with (C2F5)2POH leads to the substitution of one Cp or chloro ligand by a quasichelating unit. The novel coordination compounds were ...
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Synthesis of Unsymmetrically Substituted Phosphane Oxides (R1R2P(O)H) and Phosphinous Acids (R1R2POH)
Chemistry: A European Journal, 2014Co-Authors: Nadine Allefeld, Nikolai Ignat'ev, Michael Grasse, Berthold HogeAbstract:Invited for the cover of this issue is the group of Berthold Hoge at the University of Bielefeld. The image depicts the delicate balance between the unusual form of a Phosphinous Acid with respect to the corresponding phosphane oxide tautomer by the influence of electron-withdrawing groups. Read the full text of the article at 10.1002/chem.201402425.
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air stable and catalytically active Phosphinous Acid transition metal complexes
Organometallics, 2012Co-Authors: Boris Kurscheid, Lhoussaine Belkoura, Berthold HogeAbstract:Secondary phosphane oxides R2P(O)H are most frequently used as preligands for Phosphinous Acid R2POH (R = alkyl, aryl) transition-metal complexes, which are very efficient catalysts for cross-coupling reactions. To investigate the influence of electron-deficient substituents on the catalytic activity, the coordination properties of bis(trifluoromethyl)-, bis(pentafluoroethyl)-, and bis[2,4-bis(trifluoromethyl)phenyl]Phosphinous Acid toward catalytically relevant metals, such as palladium and platinum, are studied. The novel Phosphinous Acid palladium complexes reveal a high catalytic activity in Heck and Suzuki cross-coupling reactions. Because of the strong dependence of these processes on the reaction conditions, a systematic solvent and base screening with 1-bromo-3-fluorobenzene and phenyl boronic Acid as model reactants is performed. The most efficient solvent/base system consists of 2-propanol and potassium phosphate, providing a full conversion and a TON of around 10 000 after 20 h at room temperat...
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air stable platinum and palladium complexes featuring bis 2 4 bis trifluoromethyl phenyl Phosphinous Acid ligands
Chemistry: A European Journal, 2011Co-Authors: Boris Kurscheid, Beate Neumann, Hans-georg Stammler, Berthold HogeAbstract:: Secondary phosphane oxides, R(2)P(O)H, are commonly used as preligands for transition-metal complexes of Phosphinous Acids, R(2)P-OH (R=alkyl, aryl), which are relevant as efficient catalysts in cross-coupling processes. In contrast to previous work by other groups, we are interested in the ligating properties of an electron-deficient Phosphinous Acid, (R(f))(2)P-OH, bearing the strongly electron-withdrawing and sterically demanding 2,4-bis(trifluoromethyl)phenyl group towards catalysis-relevant metals, such as palladium and platinum. The preligand bis[2,4-bis(trifluoromethyl)phenyl]phosphane oxide, (R(f))(2)P(O)H, reacts smoothly with solid platinum(II) dichloride yielding the trans-configured Phosphinous Acid platinum complex trans-[PtCl(2)({2,4-(CF(3))(2)C(6)H(3)}(2)POH)(2)]. The deprotonation of one Phosphinous Acid ligand with an appropriate base leads to the cis-configured monoanion complex cis-[PtCl(2)({2,4-(CF(3))(2)C(6)H(3)}(2)PO)(2)H](-), featuring the quasi-chelating Phosphinous Acid phosphinito unit, (R(f))(2)P-O-H···O=P(R(f))(2), which exhibits a strong hydrogen bridge substantiated by an O···O distance of 245.1(4) pm. The second deprotonation step is accompanied by a rearrangement to afford the trans-configured dianion trans-[PtCl(2)({2,4-(CF(3))(2)C(6)H(3)}(2)PO)(2)](2-). The reaction of (R(f))(2)P(O)H with solid palladium(II) dichloride initially yields a mononuclear palladium complex [PdCl(2)({2,4-(CF(3))(2)C(6)H(3)}(2)POH)(2)], which condenses under liberation of HCl to the neutral dinuclear palladium complex [Pd(2)(μ-Cl)(2){({2,4-(CF(3))(2)C(6)H(3)}(2)PO)(2)H}(2)]. The equilibrium between the mononuclear [PdCl(2)({2,4-(CF(3))(2)C(6)H(3)}(2)POH)(2)] and dinuclear [Pd(2)(μ-Cl)(2){({2,4-(CF(3))(2)C(6)H(3)}(2)PO)(2)H}(2)] palladium complexes is reversible and can be shifted in each direction by the addition of base or HCl, respectively. Treatment of palladium(II) hexafluoroacetylacetonate, [Pd(F(6)acac)(2)], with a slight excess of (R(f))(2)P(O)H yields the complex [Pd(F(6)acac)({2,4-(CF(3))(2)C(6)H(3)}(2)PO)(2)H]. The quasi-chelating Phosphinous Acid phosphinito unit, which is formed by the liberation of HF(6)acac, is characterized by a O···O distance of 244.1(3) pm. These transition metal complexes are stable towards air and moisture and can be stored for months without any evidence of decomposition.
Gerard Buono - One of the best experts on this subject based on the ideXlab platform.
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2 1 cycloaddition affording methylene and vinylidenecyclopropane derivatives a journey around the reactivity of metal phosphinito Phosphinous Acid complexes
Chemical Record, 2017Co-Authors: Herve Clavier, Gerard BuonoAbstract:Metal–phosphinito–Phosphinous Acid complexes are interesting catalysts exhibiting unique reactivities. In this account, we intend to provide a clear overview of palladium– and platinum–phosphinito–Phosphinous Acid complexes, their preparation from secondary phosphine oxides, and their applications in catalysis. They have been mainly used to develop [2+1] cycloadditions to afford methylenecyclopropane derivatives using norbornenes and various alkynes as partners. As a function of the catalyst, the reaction conditions, or the nature of the reagents, different synthetic transformations have been observed: [2+1] cycloadditions, giving rise to either alkylidenecyclopropanes or vinylidenecyclopropanes; tandem [2+1]/[3+2] cycloadditions, and so forth. The mechanisms of these reactions have been studied to rationalize the different reactivities observed.
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[RuCl2(η6-p-cymene)] complexes bearing Phosphinous Acid ligands: preparation, application in C–H bond functionalization and mechanistic investigations
Dalton Transactions, 2016Co-Authors: Lionel V Graux, Gerard Buono, Michel Giorgi, Herve ClavierAbstract:A series of [RuCl2(η6-p-cymene)] complexes bearing Phosphinous Acid (PA) ligands have been straightforwardly prepared from the dimer [RuCl2(p-cymene)]2 and secondary phosphine oxides (SPOs) and fully characterized. The steric parameter quantification of PAs, other L ligands and η6-p-cymene allowed a better comprehension of the coordination chemistry of these types of complexes and explained the absence of coordination in the case of bulky SPOs such as Ad2P(O)H. These complexes were tested in the C–H activation/functionalization of 2-phenylpyridine and a good activity was obtained at 80 °C for the complex exhibiting the highest steric bulk. A study on halide effects, either on the ruthenium complex or for the aryl halide partner, has also been carried out showing drastic differences. Further investigations on halide effects were performed notably by using a cationic ruthenacycle which was found to be an intermediate for the reaction. In order to rationalize the role played by the Phosphinous Acid, a mechanism involving a concerted metallation deprotonation favored by a phosphinito species has been proposed.
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rucl2 η6 p cymene complexes bearing Phosphinous Acid ligands preparation application in c h bond functionalization and mechanistic investigations
Dalton Transactions, 2016Co-Authors: Lionel V Graux, Gerard Buono, Michel Giorgi, Herve ClavierAbstract:A series of [RuCl2(η6-p-cymene)] complexes bearing Phosphinous Acid (PA) ligands have been straightforwardly prepared from the dimer [RuCl2(p-cymene)]2 and secondary phosphine oxides (SPOs) and fully characterized. The steric parameter quantification of PAs, other L ligands and η6-p-cymene allowed a better comprehension of the coordination chemistry of these types of complexes and explained the absence of coordination in the case of bulky SPOs such as Ad2P(O)H. These complexes were tested in the C–H activation/functionalization of 2-phenylpyridine and a good activity was obtained at 80 °C for the complex exhibiting the highest steric bulk. A study on halide effects, either on the ruthenium complex or for the aryl halide partner, has also been carried out showing drastic differences. Further investigations on halide effects were performed notably by using a cationic ruthenacycle which was found to be an intermediate for the reaction. In order to rationalize the role played by the Phosphinous Acid, a mechanism involving a concerted metallation deprotonation favored by a phosphinito species has been proposed.
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Palladium‐Catalyzed [2+1] Cycloadditions Affording Vinylidenecyclopropanes as Precursors of 7‐Membered Carbocycles
Advanced Synthesis & Catalysis, 2016Co-Authors: Aymeric Lepronier, Gerard Buono, Laurent Giordano, Thierry Achard, Alphonse Tenaglia, Herve ClavierAbstract:Palladium(II) acetate in association with secondary phosphine oxides provides an efficient catalytic system for [2+1] cycloadditions starting from oxanorbornene derivatives and tertiary propargyl esters giving rise to vinylidenecyclopropanes. This reaction is specific to bidentate phosphinito-Phosphinous Acid ligands generated from secondary phosphine oxides. The [2+1] cycloaddition was found broad in scope with a high tolerance to various functional groups. Moreover, vinylidenecyclopropanes were straightforwardly converted into oxabicyclo[3.2.1]oct-2-ene derivatives through a palladium-catalyzed ring-expansion. Finally, the oxa bridge cleavage of oxatricyclic compounds allows the obtention of functionalized 7-membered carbocycles.
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Chemodivergent Palladium‐Catalyzed Processes: Role of Versatile Ligands
Chemcatchem, 2015Co-Authors: Paola Nava, Herve Clavier, Gerard Buono, Laurent Giordano, Yves Gimbert, Stephane HumbelAbstract:Whereas the reaction of norbornadiene with terminal alkynes in the presence of a phosphapalladacycle catalyst leads to the formation of hydroalkynation products, the use of Phosphinous Acid–phosphinito-containing palladium complexes gives rise to formal [2+1] cycloadducts. An experimental and computational approach was employed to study the mechanisms of the palladium-promoted hydroalkynation and [2+1] cycloaddition. On the one hand, experiments highlight the crucial role of Acidolysis steps on the catalytic activities. On theother hand, DFT calculations demonstrate the specificity of the phosphinito–Phosphinous Acid ligands, that is, the non-equivalence of the two phosphorus atoms but the interchangeability of their properties. These results may have important implications for the mechanism of other palladium-catalyzed transfor- mations especially those involving phosphapalladacycles and Phosphinous Acid–phosphinito-containing palladium complexes
Christian Wolf - One of the best experts on this subject based on the ideXlab platform.
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palladium Phosphinous Acid catalyzed cross coupling of aliphatic and aromatic acyl chlorides with boronic Acids
Tetrahedron Letters, 2008Co-Authors: Kekeli Ekouekovi, Hanhui Xu, Christian WolfAbstract:Abstract The cross-coupling of aromatic and aliphatic acyl chlorides with arylboronic Acids in the presence of 2.5 mol % of (t-Bu2POH)2PdCl2 (POPd) provides rapid access to ketones that are obtained in up to 93% yield. This palladium-Phosphinous Acid-catalyzed reaction is completed within 10 min when microwave irradiation is used, and it overcomes typical drawbacks of Friedel–Crafts acylation procedures such as harsh reaction conditions, untunable regiocontrol, and low substrate scope.
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palladium Phosphinous Acid catalyzed cross coupling of aryl and acyl halides with aryl alkyl and vinylzinc reagents
Journal of Organic Chemistry, 2008Co-Authors: Hanhui Xu, Kekeli Ekouekovi, Christian WolfAbstract:Several palladium−Phosphinous Acids have been prepared and employed in cross-coupling reactions of aryl or acyl halides with aliphatic and aromatic organozinc reagents. The POPd7-catalyzed reaction of aryl halides, including electron-rich aryl chlorides, and arylzinc reagents was found to afford biaryls exhibiting alkoxy, alkylthio, amino, ketone, cyano, nitro, ester, and heteroaryl groups in 75−93% yield. Excellent results were obtained with sterically hindered substrates which gave di- and tri-ortho-substituted biaryls in up to 92% yield. Aryl halides also undergo POPd7-catalyzed aryl−vinyl and aryl−alkyl bond formation under mild conditions. Styrenes and alkylarenes were prepared in 79−93% yield from aryl halides and vinyl or alkylzinc reagents. The replacement of aryl halides by acyl halides provides access to ketones which were produced in up to 98% yield when POPd was used as catalyst. This approach overcomes the limited substrate scope, reduced regiocontrol, and low functional group tolerance of tr...
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efficient synthesis of sterically crowded biaryls by palladium Phosphinous Acid catalyzed cross coupling of aryl halides and aryl grignards
Journal of Organic Chemistry, 2008Co-Authors: Christian Wolf, Hanhui XuAbstract:A series of sterically hindered biaryls have been obtained by palladium- and nickel-Phosphinous Acid-catalyzed Kumada−Corriu cross-coupling of ortho-substituted aryl halides and Grignard reagents. This method allows formation of di- and tri-ortho-substituted biaryls in 87−98% yield under mild reaction conditions even when electron-rich aryl chlorides are used. The reaction also proceeds with aryl iodides at −20 °C, and under these conditions, functional groups that are generally not compatible with Grignard reagents are tolerated.
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Chemoselective Nucleophilic Arylation and Single-Step Oxidative Esterification of Aldehydes Using Siloxanes and a Palladium−Phosphinous Acid as a Reaction Switch
Journal of the American Chemical Society, 2006Co-Authors: Rachel Lerebours And, Christian WolfAbstract:Aldehydes and siloxanes form methyl esters in a single step through mild oxidative esterification in the presence of a palladium catalyst or, alternatively, afford secondary alcohols via TBAF-promoted arylation in the absence of a catalyst at increased temperatures under otherwise identical reaction conditions.
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chemoselective nucleophilic arylation and single step oxidative esterification of aldehydes using siloxanes and a palladium Phosphinous Acid as a reaction switch
Journal of the American Chemical Society, 2006Co-Authors: Christian WolfAbstract:Aldehydes and siloxanes form methyl esters in a single step through mild oxidative esterification in the presence of a palladium catalyst or, alternatively, afford secondary alcohols via TBAF-promoted arylation in the absence of a catalyst at increased temperatures under otherwise identical reaction conditions.
Heinz Oberhammer - One of the best experts on this subject based on the ideXlab platform.
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bis trifluoromethyl Phosphinous Acid cf3 2p o h an example of a thermally stable Phosphinous Acid synthesis gas phase structure and rotational isomers
Chemistry: A European Journal, 2006Co-Authors: Berthold Hoge, Placido Garcia, Helge Willner, Heinz OberhammerAbstract:The bis(trifluoromethyl)Phosphinous Acid, (CF3)2POH, is the only known example of a thermally stable Phosphinous Acid. Although this compound has been known since 1960, little is known about the chemistry of this extraordinary compound; this might be due to the tedious, and in some part risky, synthesis that was originally published. An improved, simple, and safe synthesis that is based on the treatment of the easily accessible (CF3)2PNEt2, with at least three equivalents of p-toluene sulfonic Acid, is presented. The reaction results in a complete conversion to the Phosphinous Acid, which is isolated in almost 90 % yield. The compound exists in an equilibrium of two POH rotational isomers, a fact which is supported by quantum chemical calculations. The relative enthalpy difference of 6.4 kJ mol−1, calculated at the B3PW91/6-311G(3d,p) level, is in excellent agreement with the experimental value of 5.9 kJ mol−1, which was determined from the temperature dependence of the (OH) bands of the two rotational isomers. The complete experimental vibrational spectra of both rotamers, their predicted vibrational spectra obtained by using quantum chemical calculations, and an attempt at photoinduced isomerization of matrix-isolated (CF3)2POH is presented. The experimental structure, obtained from an electron-diffraction study in the gas phase, is reproduced very well by ab initio and density functional theory (DFT) methods.
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Bis(trifluoromethyl)Phosphinous Acid (CF3)2P-O-H: An Example of a Thermally Stable Phosphinous Acid—Synthesis, Gas-Phase Structure, and Rotational Isomers
Chemistry: A European Journal, 2006Co-Authors: Berthold Hoge, Placido Garcia, Helge Willner, Heinz OberhammerAbstract:The bis(trifluoromethyl)Phosphinous Acid, (CF3)2POH, is the only known example of a thermally stable Phosphinous Acid. Although this compound has been known since 1960, little is known about the chemistry of this extraordinary compound; this might be due to the tedious, and in some part risky, synthesis that was originally published. An improved, simple, and safe synthesis that is based on the treatment of the easily accessible (CF3)2PNEt2, with at least three equivalents of p-toluene sulfonic Acid, is presented. The reaction results in a complete conversion to the Phosphinous Acid, which is isolated in almost 90 % yield. The compound exists in an equilibrium of two POH rotational isomers, a fact which is supported by quantum chemical calculations. The relative enthalpy difference of 6.4 kJ mol−1, calculated at the B3PW91/6-311G(3d,p) level, is in excellent agreement with the experimental value of 5.9 kJ mol−1, which was determined from the temperature dependence of the (OH) bands of the two rotational isomers. The complete experimental vibrational spectra of both rotamers, their predicted vibrational spectra obtained by using quantum chemical calculations, and an attempt at photoinduced isomerization of matrix-isolated (CF3)2POH is presented. The experimental structure, obtained from an electron-diffraction study in the gas phase, is reproduced very well by ab initio and density functional theory (DFT) methods.
Laurent Giordano - One of the best experts on this subject based on the ideXlab platform.
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Platinum–(phosphinito–Phosphinous Acid) complexes as bi-talented catalysts for oxidative fragmentation of piperidinols: an entry to primary amines
RSC Advances, 2019Co-Authors: Romain Membrat, Alexandre Vasseur, Delphine Moraleda, Alexandre Martinez, Laurent Giordano, Sabine Michaud-chevallier, Didier NuelAbstract:Platinum–(phosphinito–Phosphinous Acid) complex catalyzes the oxidative fragmentation of hindered piperidinols according to a hydrogen transfer induced methodology. This catalyst acts successively as both a hydrogen carrier and soft Lewis Acid in a one pot – two steps process. This method can be applied to the synthesis of a wide variety of primary amines in a pure form by a simple Acid–base extraction without further purification.
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platinum phosphinito Phosphinous Acid complexes as bi talented catalysts for oxidative fragmentation of piperidinols an entry to primary amines
RSC Advances, 2019Co-Authors: Romain Membrat, Alexandre Vasseur, Delphine Moraleda, Sabine Michaudchevallier, Alexandre Martinez, Laurent Giordano, Didier NuelAbstract:Platinum–(phosphinito–Phosphinous Acid) complex catalyzes the oxidative fragmentation of hindered piperidinols according to a hydrogen transfer induced methodology. This catalyst acts successively as both a hydrogen carrier and soft Lewis Acid in a one pot – two steps process. This method can be applied to the synthesis of a wide variety of primary amines in a pure form by a simple Acid–base extraction without further purification.
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Palladium‐Catalyzed [2+1] Cycloadditions Affording Vinylidenecyclopropanes as Precursors of 7‐Membered Carbocycles
Advanced Synthesis & Catalysis, 2016Co-Authors: Aymeric Lepronier, Gerard Buono, Laurent Giordano, Thierry Achard, Alphonse Tenaglia, Herve ClavierAbstract:Palladium(II) acetate in association with secondary phosphine oxides provides an efficient catalytic system for [2+1] cycloadditions starting from oxanorbornene derivatives and tertiary propargyl esters giving rise to vinylidenecyclopropanes. This reaction is specific to bidentate phosphinito-Phosphinous Acid ligands generated from secondary phosphine oxides. The [2+1] cycloaddition was found broad in scope with a high tolerance to various functional groups. Moreover, vinylidenecyclopropanes were straightforwardly converted into oxabicyclo[3.2.1]oct-2-ene derivatives through a palladium-catalyzed ring-expansion. Finally, the oxa bridge cleavage of oxatricyclic compounds allows the obtention of functionalized 7-membered carbocycles.
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Chemodivergent Palladium‐Catalyzed Processes: Role of Versatile Ligands
Chemcatchem, 2015Co-Authors: Paola Nava, Herve Clavier, Gerard Buono, Laurent Giordano, Yves Gimbert, Stephane HumbelAbstract:Whereas the reaction of norbornadiene with terminal alkynes in the presence of a phosphapalladacycle catalyst leads to the formation of hydroalkynation products, the use of Phosphinous Acid–phosphinito-containing palladium complexes gives rise to formal [2+1] cycloadducts. An experimental and computational approach was employed to study the mechanisms of the palladium-promoted hydroalkynation and [2+1] cycloaddition. On the one hand, experiments highlight the crucial role of Acidolysis steps on the catalytic activities. On theother hand, DFT calculations demonstrate the specificity of the phosphinito–Phosphinous Acid ligands, that is, the non-equivalence of the two phosphorus atoms but the interchangeability of their properties. These results may have important implications for the mechanism of other palladium-catalyzed transfor- mations especially those involving phosphapalladacycles and Phosphinous Acid–phosphinito-containing palladium complexes
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Bulky, optically active P-stereogenic phosphine-boranes from pure H-menthylphosphinates.
Journal of the American Chemical Society, 2011Co-Authors: David Gatineau, Laurent Giordano, Gerard BuonoAbstract:The transformation of readily available pure-H-menthylphosphinates into chiral Phosphinous Acid-boranes permits the elaboration of bulky P-stereogenic secondary phosphine–boranes. Taking advantage of the synthetic potential of these compounds, a broad range of hindered P-chiral tertiary phosphine–boranes has been prepared with excellent enantiomeric excesses. The utility of bulky o-tolylphosphines was illustrated by the synthesis of a rare enantiopure phosphapalladacycle (SP,SP)-12.