Chemoselective Reactions of the Phosphino Enolate Li[Ph2PCH C( O)NPh2] with Ph2P−Cl and M−Cl Bonds (M = Pd, Pt). Coordination Properties of the New Functional Diphosphine Ligand (Ph2P)2CHC(O)NPh2. Hemilabile Behavior of [Cu2{(Ph2P)2CHC(O)NPh2-P,P,O}2](BF4)2. Reactivity and Molecular Structure of [(8-mq)Pd{Ph2PCH C( O)NPh2

Andrieu, Jacques; Braunstein, Pierre; Tiripicchio, António; Ugozzoli, Franco

doi:10.1021/ic951412p

Cited by 33 publications

(31 citation statements)

References 35 publications

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“…The latter complex was assigned to the [PtCl 3 ( 2a )] complex 4 , which was independently prepared by treating [PtCl 2 (NCPh) 2 ] with one equivalent of compound 2a (Scheme ), and by using reaction conditions similar to those described for a platinum analogue complex 18. Because the imidazolium‐2‐phosphane was formed in the above experiment in spite of the platinum coordination, which masks the lone pair of electrons on the phosphorus atom in chlorodiphenylphosphane, we can suggest that PR 2 Cl likely reacts as an electrophilic reagent19 toward imidazolium‐2‐carboxylate (Scheme , path 3). This assumption is supported by the lack of reactivity when the less electron rich carboxylic acid [MMIM‐2‐CO 2 H](BF 4 ) is used under the conditions described for imidazolium‐2‐carboxylate (Scheme , path 1).…”

Section: Resultsmentioning

confidence: 99%

Straightforward Synthesis of Donor‐Stabilised Phosphenium Adducts from Imidazolium‐2‐carboxylate and Their Electronic Properties

et al. 2007

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Cationic imidazolium‐2‐phosphanes were obtained by the addition of a chlorophosphane (R2PCl, R = Ph, iPr or Cy) to 1,3‐dimethylimidazolium‐2‐carboxylate without the need for a purification step. An additional anion exchange reaction with KPF6 led to the corresponding halide‐free ligands in excellent yields. The molecular structure of one of them was examined both in the solid state and in solution. The lone pair of electrons on the phosphorus atom is not delocalised to the imidazolium fragment and thus remains available for further metal coordination. As such compounds can be described as phosphenium cations stabilised by a N‐heterocarbene donor base, the electronic properties of the Lewis acceptor phosphorus centre was evaluated upon nickel tricarbonyl coordination, and the properties are surprisingly similar to those found for phosphites. The stronger π‐acceptor character of these imidazolium‐2‐phosphanes relative to that of neutral tertiary phosphanes can thus explain the higher catalytic activities observed with the corresponding rhodium complexes in styrene hydroformylation reactions. Additionally, a preliminary study of platinum coordination chemistry indicated that the steric demand of 1,3‐dimethylimidazolium‐2‐phosphanes is comparable to mixed arylalkylphosphanes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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Section: Resultsmentioning

confidence: 99%

Straightforward Synthesis of Donor‐Stabilised Phosphenium Adducts from Imidazolium‐2‐carboxylate and Their Electronic Properties

et al. 2007

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“…A solvent molecule may also displace the kinetically more labile Z→M bond, as shown with the Cu I complexes in Equation (14). 83 In the absence of a donor solvent, only hemilabile behavior of the type shown in Scheme is observed. By exploiting their spectroscopic properties, Ru II bipyridyl complexes containing a hemilabile phosphane ether ligand have been used as sensors for molecules such as DMSO, MeCN, or SMe 2 84…”

Section: Hemilabile Ligandsmentioning

confidence: 99%

“…As an extension of our studies on the coordination chemistry of, and catalysis with, the ligands β ‐phosphino‐ketones,67, 204–206 ‐ester,15 ‐acids, or ‐amides,83, 90 of type 34 , we became interested in using oxazoline moieties for the design of new functional phosphane ligands.…”

Section: Hemilabile Phosphorus–oxazoline Hybrid Ligandsmentioning

confidence: 99%

Hemilability of Hybrid Ligands and the Coordination Chemistry of Oxazoline-Based Systems

Braunstein

Naud

2001

Angew. Chem. Int. Ed.

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943

618

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Ligand design is becoming an increasingly important part of the synthetic activity in chemistry. This is of course because of the subtle control that ligands exert on the metal center to which they are coordinated. Ligands which contain significantly different chemical functionalities, such as hard and soft donors, are often called hybrid ligands and find increasing use in molecular chemistry. Although the interplay between electronic and steric properties has long been recognized as essential in determining the chemical or physical properties of a complex, predictions remain very difficult, not only because of the considerable diversity encountered within the Periodic Table—different metal centers will behave differently towards the same ligand and different ligands can completely modify the chemistry of a given metal—but also because of the small energy differences involved. New systems may—even through serendipity—allow the emergence of useful concepts that can gain general acceptance and help design molecular structures orientated towards a given property. The concept of ligand hemilability, which finds numerous illustrations with hybrid ligands, has gained increased acceptance and been found to be very useful in explaining the properties of metal complexes and in designing new systems for molecular activation, homogeneous catalysis, functional materials, or small‐molecule sensing. In the field of homogeneous enantioselective catalysis, in which steric and/or electronic control of a metal‐mediated process must occur in such a way that one stereoisomer is preferentially formed, ligands containing one or more chiral oxazoline units have been found to be very valuable for a wide range of metal‐catalyzed reactions. The incorporation of oxazoline moieties in multifunctional ligands of increasing complexity makes such ligands good candidates to display hemilabile properties, which until recently, had not been documented in oxazoline chemistry. Herein, we briefly recall the definition and scope of hemilabile ligands, present the main classes of ligands containing one or more oxazoline moieties, with an emphasis on hybrid ligands, and finally explain why the combination of these two facets of ligand design appears particularly promising.

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“…Ein Lösungsmittelmolekül kann die kinetisch labile Z→M‐Bindung ebenfalls spalten, wie am Cu I ‐Komplex in Gleichung (14) gezeigt wird 83. Ohne Donorsolventien tritt das in Schema skizzierte hemilabile Verhalten auf.…”

Section: Hemilabile Ligandenunclassified

“…Zur weiteren Untersuchung bezüglich der Koordinationschemie und des katalytischen Verhaltens von Liganden des Typs 34 , d. h. von β ‐Phosphanylketonen,67, 204–206 ‐estern,15 ‐carbonsäuren und ‐amiden,83, 90 beschäftigten wir uns mit dem Design neuer Phosphanliganden mit Oxazolinresten. …”

Section: Hemilabile Phosphor‐oxazolin‐hybridligandenunclassified

Hemilabilität von Hybridliganden und die Koordinationschemie von Oxazolinliganden

2001

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Das Ligandendesign gewinnt auf dem Gebiet der chemischen Synthese immer mehr an Bedeutung, denn mit Hilfe von speziellen Liganden lassen sich die Eigenschaften von Komplexen in vielfältiger Weise beeinflussen. Liganden mit verschiedenen Funktionalitäten, z. B. solche mit harten und weichen Donoren, werden oft als Hybridliganden bezeichnet und zunehmend in der Molekülchemie verwendet. Zwar ist schon lange bekannt, dass die elektronischen und sterischen Eigenschaften der Koordinationssphäre eines Komplexes sehr eng mit dessen chemischen und physikalischen Eigenschaften zusammenhängen, doch ist eine Voraussage des Verhaltens von Liganden schwierig, nicht nur wegen der bei diesen Veränderungen auftretenden geringen Energiedifferenzen, sondern auch wegen der beträchtlichen Diversität innerhalb des Periodensystems – ein bestimmter Ligand kann sich gegenüber verschiedenen Metallen ganz unterschiedlich verhalten, und der Austausch eines Liganden gegen einen anderen in einem gegebenen Metallkomplex kann dessen Chemie vollkommen verändern. Neue Systeme könnten, auch rein zufällig, zu nützlichen, allgemein gültigen Konzepten führen, mit deren Hilfe Molekülstrukturen mit bestimmten Eigenschaften maßgeschneidert werden können. Einige Eigenschaften von zahlreichen Metallkomplexen mit Hybridliganden lassen sich mit der „Hemilabilität“ dieser Liganden erklären – einem sehr nützlichen Konzept, um die Eigenschaften der Metallkomplexe zu deuten und um neue Systeme für die molekulare Aktivierung und die homogene Katalyse sowie funktionelle Materialien und Sensoren für niedermolekulare Verbindungen zu entwerfen. In der homogenen enantioselektiven Katalyse wird in einem metallvermittelten Prozess durch sterische und/oder elektronische Kontrolle ein Stereoisomer bevorzugt gebildet. Die Verwendung von Liganden mit einem oder mehreren chiralen Oxazolinresten in diesen metallkatalysierten Reaktionen führte in vielen Fällen zu guten Ergebnissen. Die Einführung von Oxazolinresten in multifunktionelle Liganden erhöht deren Komplexität und die Wahrscheinlichkeit, dass hemilabile Eigenschaften auftreten, die bis vor kurzem in der Oxazolinchemie noch nicht beobachtet worden sind. In diesem Übersichtsartikel werden wir zunächst kurz auf die Definitionen und die Anwendungsmöglichkeiten hemilabiler Liganden eingehen, dann die Hauptklassen der Liganden mit einem oder mehreren Oxazolinresten vorstellen, wobei der Schwerpunkt auf den Hybridliganden liegt, und abschließend erläutern, warum die Kombination dieser beiden Aspekte des Ligandendesigns besonders viel versprechend erscheint.

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Cited by 33 publications

References 35 publications

Straightforward Synthesis of Donor‐Stabilised Phosphenium Adducts from Imidazolium‐2‐carboxylate and Their Electronic Properties

Straightforward Synthesis of Donor‐Stabilised Phosphenium Adducts from Imidazolium‐2‐carboxylate and Their Electronic Properties

Hemilability of Hybrid Ligands and the Coordination Chemistry of Oxazoline-Based Systems

Hemilabilität von Hybridliganden und die Koordinationschemie von Oxazolinliganden

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