Synthesis and Characterization of an Unsymmetrical 1,2-Diphosphinoethanide Complex

Förster, Daniela; Nieger, Martin; Gudat, Dietrich

doi:10.1021/om200069t

Cited by 10 publications

(11 citation statements)

References 17 publications

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“…Both cyclohexyl groups are oriented in a mutually transoid arrangement with respect to the P-Cl bond, presumably in order to minimize intramolecular steric interactions, and lie thus on the same side of the central ring. The P-Cl distance of 2.534(1)Å is similar to those in other P-chloro-N-alkyl-diazaphospholenes (2.567(1)-2.692(4)Å [30,31]) but longer than in N-aryl derivatives (2.243(1)-2.362(1)Å [27,30,31]). …”

Section: Resultssupporting

confidence: 71%

“…The observed isomer ratio of 1:1 suggests that both diastereomers have nearly equal stability and formation kinetics. Formation of addition products with non-uniform configuration of the C 2 -backbone had previously been observed in other diphosphination reactions of electronpoor alkenes [26] and does not necessarily point to a low enantioselectivity of the addition step itself but may rather be explained as a consequence of the configurational lability of the product, which allows easy configuration epimerization of the backbone carbon atoms [26,27].…”

Section: Resultsmentioning

confidence: 61%

“…This finding contrasts the behavior of diphosphination products derived from Nheterocyclic diphosphines and maleic or fumaric esters, where metal coordination of 1,2-bisphosphines induces configuration epimerization at the backbone carbon atoms, and where a single, energetically favored diastereomer is obtained [26]. In regard of the proven configurational lability of comparable 1,2-bisphosphine ligands [26,27], and the finding that secondary phosphines are likewise sensitive toward configuration inversion [36 -39], we consider it likely that the apparent reluctance of the different diastereomers of 12 and 13 to isomerize to a single predominant isomer is not attributable to kinetic inhibition, but reflects the fact that the individual diastereomers remain close in energy.…”

Section: Resultsmentioning

confidence: 66%

“…Subsequent reaction with (cod)PdCl 2 resulted in the replacement of the 31 P{ 1 H} NMR signals of 12 by four new sets of AX patterns which display strong deshieldings (δ 31 P = 120.0 -121.0 for PN 2 and 27.6 -31.9 for P(H)Men units) and somewhat increased values of J PP (26)(27)(28)(29)(30)(31)(32)(33). Efforts to isolate individual components remained unsuccessful.…”

Section: Resultsmentioning

confidence: 99%

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On the Synthesis and Addition Reactions of Chiral N-Heterocyclic Diphosphines

Förstera

Hartenbach

Nieger

et al. 2012

Zeitschrift Für Naturforschung B

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Reaction of chiral N-heterocyclic chlorophosphines with lithium diphenylphosphide or of achiral N-heterocyclic chlorophosphines with optically active lithium menthyl phosphide produces chiral N-heterocyclic diphosphines which can be utilized in subsequent diphosphination reactions with activated alkenes or alkynes. The reaction with alkynes proceeds stereospecifically to produce Zethylene-1,2-bisphosphines which are readily converted to nickel(II) or palladium(II) complexes. Reactions with alkenes are synthetically less useful as the addition proceeds without any chiral induction at the newly formed stereocenters to yield inseparable mixtures of diastereomeric products. The molecular structures of chiral Z-ethylene-1,2-bisphosphine complexes and of a chiral N-heterocyclic chlorophosphine have been determined by single-crystal X-ray diffraction.

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Section: Resultssupporting

confidence: 71%

Section: Resultsmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 66%

Section: Resultsmentioning

confidence: 99%

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On the Synthesis and Addition Reactions of Chiral N-Heterocyclic Diphosphines

Förstera

Hartenbach

Nieger

et al. 2012

Zeitschrift Für Naturforschung B

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“…52 Reactions of phosphino-DAPs with electron poor alkenes and alkynes occur via addition to the multiple bonds ("phosphino-phosphination") and offer one-step access to unsymmetrical bis-phosphines from simple precursors (Scheme 8). 22,23,47,48 As addition to di-activated alkynes is also known for other types of diphosphines, 49 the special aspect here is that the unique reactivity of phosphino-DAPs widens the scope to include terminal alkynes as well as alkenes as new substrate classes. Additions to unsymmetrical alkenes and alkynes proceed regiospecifically in accordance with the P-P bond pre-polarization, and those to internal alkynes are Z-stereospecific.…”

Section: Perspectivementioning

confidence: 99%

A very peculiar family of N-heterocyclic phosphines: unusual structures and the unique reactivity of 1,3,2-diazaphospholenes

Gudat

2016

Dalton Trans.

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This Perspective gives an account of the peculiar electronic and molecular structures of N-heterocyclic phosphines featuring either a single 1,3,2-diazaphospholene (DAP) ring with an exocyclic P-substituent X or two DAP rings linked by a P-P bond (bis-diazaphospholenyls), respectively, and their impact on the chemical properties of these molecules. The bonding situation in simple DAPs is epitomized by strong hyperconjugation between endocyclic π-type electrons and the exocyclic P-X bond. This interaction may induce a perceptible ionic polarization of the P-X bond which can persist even in the limit of a vanishing electronegativity gradient between P and X, and becomes visible in unusual geometric distortions of molecular structures and a unique chemical behaviour. Structural distortions are particularly evident in bond lengthening effects in P-halogen and P-phosphino derivatives R2P-DAP (with R2P ≠ DAP) which span the whole range from covalent molecules to contact ion pairs with a close relation to frustrated Lewis-pairs. The most significant impact on the chemical properties is found for P-phosphino- and P-hydrogen derivatives where reactions at substantially accelerated rates or totally new reaction modes can be observed, and new stoichiometric and first catalytic processes exploiting these features are currently emerging. The recently discovered bis-diazaphospholenyls differ from the simple derivatives as their central bond remains unpolarised as a consequence of the symmetric molecular structure. The occurrence of low-energy P-P bond homolysis that was nonetheless observed in one case is according to the results of thermochemical studies of P-P bond fission reactions attributable to the effects of steric congestion and induces chemical reactivity that can be considered complementary to that of the simple R2P-DAPs. Some concluding remarks will pay attention to a facet of DAP reactivity that has so far been widely neglected but is currently receiving increasing attention, namely well-defined ring-opening processes.

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Diazaphospholene Chemistry

Gudat¹

2018

Encyclopedia of Inorganic and Bioinorganic Chemistry

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Diazaphospholenes are N‐heterocyclic phosphines that can be derived from N‐heterocyclic carbenes by formally replacing the divalent carbon atom by a P–X unit consisting of a tervalent phosphorus atom and an exocyclic substituent X. This arrangement provides a very peculiar electronic structure that is characterized by an exceptionally strong hyperconjugation between delocalized π‐electrons in the ring and the σ*(P–X) orbital and results in a considerable ionic polarization of the exocyclic bond with a concomitant increase of negative partial charge on X. The effect persists even in unpolar P–X bonds and induces unprecedented chemical reactivity like a marked polarization of homonuclear bonds to phosphorus‐based substituents, which immensely facilitates bond activation reactions, and a reversal of the polarity (“Umpolung”) of the P–H bonds in secondary diazaphospholenes, which gives rise to a hydride behavior unprecedented for phosphines. The emerging exploitation of these features in diverse areas of synthetic chemistry sparked various applications of diazaphospholenes both as stoichiometric reagents and as organocatalysts. It is the aim of this article to give a comprehensive overview on the chemistry of diazaphospholenes, starting with a discussion of their specific electronic structure, and addressing their synthesis, principal reaction patterns, and applications as reagents in stoichiometric reactions and organocatalysts in metal‐free catalytic transformations. A concluding section will focus on ligand‐centered reactions of diazaphospholenes with exocyclic transition metal substituents (“metallo‐diazaphospholenes”) and their application in catalysis.

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Synthesis and Characterization of an Unsymmetrical 1,2-Diphosphinoethanide Complex

Cited by 10 publications

References 17 publications

On the Synthesis and Addition Reactions of Chiral N-Heterocyclic Diphosphines

On the Synthesis and Addition Reactions of Chiral N-Heterocyclic Diphosphines

A very peculiar family of N-heterocyclic phosphines: unusual structures and the unique reactivity of 1,3,2-diazaphospholenes

Diazaphospholene Chemistry

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