(+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene: Properties & Uses
(+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene: Properties & Uses
(+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene is a sterically defined, C2-symmetric chiral bisphosphine ligand widely employed in transition-metal-catalyzed asymmetric transformations, particularly enantioselective hydrogenation reactions.
- IUPAC Name
- (+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene
- Strem Catalog Number
- 15-0092
- Ligand Class
- C2-symmetric chiral bisphosphine
- Key Application
- Asymmetric hydrogenation and enantioselective catalysis
- Stereochemistry
- (2S,5S) configuration at both phospholane rings
- Coordination Mode
- Bidentate phosphine donor via two P atoms
Overview and Structural Features
(+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene, commonly referred to as (+)-BisP* or Me-BPE, belongs to the family of electron-rich, C2-symmetric chiral bisphosphine ligands. Its molecular framework consists of an ortho-phenylene backbone bearing two (2S,5S)-2,5-dimethylphospholane rings, one at each phosphorus atom. This rigid yet conformationally well-defined architecture positions the two phosphorus donor atoms in a cis-like arrangement ideal for chelation to transition metals.
The electron-donating alkyl substituents on the phospholane rings render the phosphorus centers highly nucleophilic, promoting strong coordination to late transition metals such as rhodium, ruthenium, and iridium. The stereogenic centers at the 2- and 5-positions of each phospholane ring create a well-defined chiral environment in the immediate vicinity of the metal center, which is essential for achieving high enantioselectivity in catalytic cycles.
Applications in Asymmetric Catalysis
(+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene is most extensively utilized as a chiral ligand in rhodium- and ruthenium-catalyzed asymmetric hydrogenation reactions. When complexed with [Rh(COD)₂]BF₄ or analogous precursors, the resulting catalyst system is capable of reducing a broad range of prochiral substrates—including dehydroamino acid derivatives, enamides, itaconic acid derivatives, and β-keto esters—with excellent enantioselectivities.
Beyond hydrogenation, the ligand has been explored in asymmetric hydroboration, hydrosilylation, and other metal-mediated enantioselective processes. Its strong σ-donor character and constrained chelate ring geometry contribute to catalyst stability and reproducibility across diverse reaction conditions. Researchers selecting this ligand benefit from its well-documented performance as a benchmark chiral bisphosphine in method development and substrate scope studies.
Handling, Storage, and Safety Considerations
As a phosphine-containing compound, (+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene is air- and moisture-sensitive. Oxidation of the phosphorus centers upon exposure to atmospheric oxygen can diminish catalytic performance; therefore, all handling should be performed under an inert atmosphere (nitrogen or argon) using standard Schlenk or glovebox techniques.
The compound should be stored in a tightly sealed container under inert gas at low temperature (typically 2–8 °C or as specified by the supplier) and protected from light. Stock solutions prepared in anhydrous, degassed solvents such as tetrahydrofuran, dichloromethane, or toluene should be prepared and transferred under inert conditions. Appropriate personal protective equipment—including gloves, safety glasses, and laboratory coat—should be worn during handling. Consult the Safety Data Sheet (SDS) provided by Aladdin Scientific for comprehensive hazard information before use.
Purity, Specifications, and Quality Assurance
Aladdin Scientific offers (+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene (SKU: B281816) sourced with reference to Strem Catalog Number 15-0092. Researchers are advised to verify the specific purity grade, enantiomeric excess (ee), and analytical characterization data—such as ³¹P NMR, optical rotation, and HPLC purity—on the product datasheet before use, as these parameters directly impact catalytic outcomes.
For asymmetric catalysis applications, high enantiomeric purity is paramount. Any compromise in ee of the ligand will be directly reflected in reduced enantioselectivity of the catalytic product. Procurement teams should request certificates of analysis (CoA) confirming optical rotation values and chromatographic purity with each lot. Contact Aladdin Scientific technical support for bulk quantities, custom specifications, or additional characterization data.
Frequently asked questions
What transition metals is (+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene most commonly used with?
This ligand is most frequently employed with rhodium(I) and ruthenium(II) precursors to form highly active asymmetric hydrogenation catalysts. Iridium-based complexes have also been reported in the literature for specific substrate classes.
How should I prepare a catalyst solution using this bisphosphine ligand?
All operations should be conducted under inert atmosphere (N₂ or Ar) using Schlenk techniques or a glovebox. Dissolve the ligand and an appropriate metal precursor (e.g., [Rh(COD)₂]BF₄) in a dry, degassed solvent, typically in a 1:1 or slight excess ligand-to-metal ratio, then allow the complex to form at room temperature or as specified by your protocol before adding substrate.
Why is enantiomeric excess (ee) of the ligand critical for asymmetric hydrogenation?
The chiral environment generated around the metal center—which controls the facial selectivity of substrate binding and hydride delivery—is directly determined by the stereochemical purity of the bisphosphine ligand. A ligand with lower ee will produce a mixture of enantiomeric metal complexes, reducing the overall enantioselectivity of the catalytic reaction and compromising product ee.
What solvents are suitable for dissolving (+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene?
Common anhydrous, degassed solvents such as tetrahydrofuran (THF), dichloromethane (DCM), toluene, and methanol are generally suitable. The choice of solvent may also influence catalyst activity and selectivity, so solvent screening is recommended when optimizing new reactions.
References
- Burk, M. J. Modular Phospholane Ligands in Asymmetric Catalysis. Acc. Chem. Res. 2000, 33, 363–372. doi:10.1021/ar990060s
- Strem Chemicals Product Catalog, Entry 15-0092, (+)-1,2-Bis((2S,5S)-2,5-dimethylphospholano)benzene.
- Gridnev, I. D.; Imamoto, T. On the Mechanism of Stereoselection in Rh-Catalyzed Asymmetric Hydrogenation: A General Approach for Predicting the Sense of Enantioselectivity. Acc. Chem. Res. 2004, 37, 633–644. doi:10.1021/ar030156e
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