Terminal Phosphanido Rhodium Complexes Mediating Catalytic P?P and P?C Bond Formation

Complexes with terminal phosphanido (M PR₂) functionalities are believed to be crucial intermediates in new catalytic processes involving the formation of P P and P C bonds. We showcase here the isolation and characterization of mononuclear phosphanide rhodium complexes ([RhTp(H)(PR₂)L]) that result from the oxidative addition of secondary phosphanes, a reaction that was also explored computationally. These compounds are active catalysts for the dehydrocoupling of PHPh₂ to Ph₂P PPh₂. The hydrophosphination of dimethyl maleate and the unactivated olefin ethylene is also reported. Reliable evidence for the prominent role of mononuclear phosphanido rhodium species in these reactions is also provided.     

Synthesis of Dendritic BINAP Ligands and Their Applications in Asymmetric Hydrogenation

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Novel Chiral Aminophosphine Ligand: Synthesis and Application in Asymmetric Catalytic Hydrogenation Reaction

ＩｎｔｒｏｄｕｃｔｉｏｎＴｒａｎｓｉｔｉｏｎｍｅｔａｌｃｏｍｐｌｅｘｃａｔａｌｙｚｅｄａｓｙｍｍｅｔｒｉｃｒｅａｃｔｉｏｎｓｈａｖｅａｔｔｒａｃｔｅｄｇｒｅａｔａｔｔｅｎｔｉｏｎｂｅｃａｕｓｅｏｆｔｈｅｉｒｈｉｇｈｅｆｆｉｃｉｅｎｃｙｆｏｒｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆｅｎａｎｔｉｏｍｅｒｉｃａｌｌｙｐｕｒｅｃｏｍｐｏｕｎｄｓ,ａｎｄｇｒｅａｔｅｆｆｏｒｔｓｈａｖｅｂｅｅｎｍａｄｅｔｏｗａｒｄｓｔｈｅｄｅｓｉｇｎａｎｄｓｙｎｔｈｅｓｉｓｏｆｎｅｗｃｈｉｒａｌｌｉｇａｎｄｓｆｏｒｔｈｉｓｐｕｒｐ…     

Catalytic C?C,C?N,and C?O Ullmann‐Type Coupling Reactions

Copper‐catalyzed Ullmann condensations are key reactions for the formation of carbon–heteroatom and carbon–carbon bonds in organic synthesis. These reactions can lead to structural moieties that are prevalent in building blocks of active molecules in the life sciences and in many material precursors. An increasing number of publications have appeared concerning Ullmann‐type intermolecular reactions for the coupling of aryl and vinyl halides with N, O, and C nucleophiles, and this Minireview highlights recent and major developments in this topic since 2004.     

P?N ligands in lanthanide chemistry

The coordination chemistry of inorganic amides in Group 3 and lanthanide chemistry is discussed. Three different ligand systems (phosphino‐amides, bis(phosphino)amides, and bis(phosphinimino)methanides) that consist of one or more P N units were used. In this series the steric demand of the ligands is increased in a stepwise fashion and the negative charge is delocalized over more atoms. These properties were used in the design of new lanthanide complexes. For all three compounds the synthesis of the alkali metal derivatives is reported first, followed by the reaction of the alkali metal salts with various lanthanide trichlorides. Further reactions of the obtained lanthanide complexes as well as their application as catalysts are discussed. Most of the reported complexes show a dynamic behavior in solution. In phosphinoamide and bis(phosphino)amide complexes, in which the phosphorus atom is in oxidation state +3, there is always a weak coordination of the phosphorus atom to the lanthanide atom observed. In bis(phosphinimino)methanide complexes, in which the phosphorus atom is in oxidation state +5, no such interaction is noticeable. Instead a weak coordination of the methine atom to the center metal can be seen in the solid state. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:514–520, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10096     

Synthesis of New Chiral Phosphine Ligands and Their Application in Asymmetric Hydrogenation of Ketones

The design of new chiral ligands is the key in the development of transition metal catalyzed asymmetric synthesis. Many chiral diphosphine ligands have been prepared and applied in asymmetric catalytic reactions with excellent enantioselectivities. Among the chiral diphosphine ligands that have been reported, the atropisomeric C2-symmetric phosphines with a biaryl scaffold initiated by Noyori and co-workers with BINAP were found to have the widest application in the transition metal catalyze…     

P?C‐Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine–Boranes

{Rh(xantphos)}‐based phosphido dimers form by P C activation of xantphos (4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene) in the presence of amine–boranes. These dimers are active dehydrocoupling catalysts, forming polymeric [H₂BNMeH]_n from H₃B⋅NMeH₂ and dimeric [H₂BNMe₂]₂ from H₃B⋅NMe₂H at low catalyst loadings (0.1 mol %). Mechanistic investigations support a dimeric active species, suggesting that bimetallic catalysis may be possible in amine–borane dehydropolymerization.     

Synthesis,Crystal Structure and Catalytic Activity Palladium (Ⅱ) Complexes Containing Bulky Azole Ligands

Bulky azole ligands in combination with PdCl_2 provide three new palladium(II) complexes. All these complexes, as pre-catalysts, have high catalytic efficiency for the Suzuki-Miyaura cross-coupling reactions of sterically hindered aryl chlorides and good to high yields are obtained with low catalysts loadings(0.1 mol%) under mild conditions in air.     

Chiral Schiff Base Ligands Containing Ferrocene and Pyridine Units for Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation

ChiralSchiffbasecomplexesareveryefficientforawiderangeofreactions ,includingexpoxida tion[1] ,epoxideringopening[2 ] ,Diels Alderreac tion[3 ] ,aldolreaction[4 ] ,etc .However ,thereareonlyfewexamplesofP NchelateSchiffbasesbeingusedasthechiralligandsintheasymmetrictransferhydrogenationofketones .Recently ,Gaoetal[5] re portedaseriesofP ,N ,N ,PSchiffbaseligandsthathaverelativelylowenantioselectivityintheasymmet rictransferhydrogenationofketones .Here ,were portthesynthesisofaseriesofnewP …     

Concerted Interaction between Pnicogen and Halogen Bonds in XCl?FH2P?NH3 (X=F,OH, CN,NC, and FCC)

We analyze the interplay between pnicogen‐bonding and halogen‐bonding interactions in the XCl? FH₂P? NH₃ (X=F, OH, CN, NC, and FCC) complex at the MP2/aug‐cc‐pVTZ level. Synergetic effects are observed when pnicogen and halogen bonds coexist in the same complex. These effects are studied in terms of geometric and energetic features of the complexes. Natural bond orbital theory and Bader’s theory of “atoms in molecules” are used to characterize the interactions and analyze their enhancement with varying electron density at critical points and orbital interactions. The physical nature of the interactions and the mechanism of the synergetic effects are studied using symmetry‐adapted perturbation theory. By taking advantage of all the aforementioned computational methods, the present study examines how both interactions mutually influence each other.     

Oxindole Synthesis by Direct Coupling of C?H and C?H Centers

An sp ² /sp ³ get‐together : A novel and efficient method can be used to synthesize 3,3‐disubstitued oxindoles by the direct intramolecular oxidative coupling of an aryl C? H and a C? H center (see scheme; DMF=N,N‐dimethylformamide).

     

Catalytic C?F Activation and Hydrodefluorination of Fluoroalkyl Groups

A powerful fluoride trap : The extremely Lewis acidic silyl cation [Et₃Si]⁺ is an active catalyst for the hydrodefluorination of fluoroalkyl groups at room temperature (see example). The carborane anion [CHB₁₁H₅Cl₆]^? plays an essential role in the catalytic cycle as a weakly coordinating anion that stabilizes cationic intermediates.