meso-1,2-Diphenylethylenediamine: Properties, Uses & Handling Guide

meso-1,2-Diphenylethylenediamine is a stereochemically defined vicinal diamine widely used as a chiral ligand precursor and versatile building block in asymmetric catalysis and metal-complex synthesis.

Chemical Name

meso-1,2-Diphenylethylenediamine

Aladdin SKU

M473727

Molecular Formula

C14H16N2

Molecular Weight

212.29 g/mol

Stereochemistry

meso form (R,S configuration); achiral molecule with an internal plane of symmetry

Appearance

White to off-white crystalline solid

Key Applications

Chiral ligand synthesis, asymmetric catalysis, Schiff base formation, metal chelation

Chemical Identity and Physicochemical Properties

meso-1,2-Diphenylethylenediamine (CAS number to be confirmed; Aladdin SKU M473727, cross-reference Sigma-Aldrich 458511) is a vicinal diamine bearing two phenyl substituents on adjacent carbons. The meso designation indicates that the two stereocenters carry opposite absolute configurations (R and S), resulting in an internal plane of symmetry that renders the overall molecule achiral despite the presence of two chiral carbons.

The molecular formula is C₁₄H₁₆N₂ with a molecular weight of approximately 212.29 g/mol. The compound typically presents as a white to off-white crystalline solid at room temperature. The two primary amine groups (–NH₂) confer moderate basicity and excellent nucleophilicity, making the molecule highly reactive toward carbonyl-containing electrophiles such as aldehydes, ketones, and acyl chlorides. Its aromatic phenyl groups contribute rigidity and hydrophobicity, influencing both solubility and coordination geometry when employed as a metal-binding ligand.

Note for procurement: Verify CAS number, melting point, and purity specification with the current Aladdin certificate of analysis (CoA) for lot-specific data prior to use.

Applications in Asymmetric Catalysis and Ligand Design

Despite being achiral itself, meso-1,2-diphenylethylenediamine is a valuable starting material for the preparation of chiral salen-type Schiff base ligands and other nitrogen-donor chelates. Condensation of the two amine groups with chiral aldehydes or salicylaldehydes yields unsymmetrical or symmetrical tetradentate Schiff base ligands that are subsequently employed to complex transition metals such as Co, Mn, Cu, and Ni for enantioselective reactions.

The compound also serves as a scaffold for constructing chiral phase-transfer catalysts and organocatalysts. Monoprotection or mono-acylation strategies allow chemists to introduce a single functional handle while retaining one free amine for further elaboration, expanding the structural diversity accessible from this core.

In metal-complex chemistry, the 1,2-diamine motif adopts a five-membered chelate ring geometry upon coordination, providing thermodynamic stability and well-defined steric environments around the metal center. The flanking phenyl groups can engage in additional non-covalent interactions (e.g., π–π stacking) with substrate molecules, potentially enhancing enantioselectivity.

Safe Handling, Storage, and Waste Disposal

Hazard overview: Primary aliphatic/benzylic diamines can be skin and eye irritants and may cause sensitization upon repeated exposure. Always consult the current Safety Data Sheet (SDS) supplied by Aladdin Scientific before handling meso-1,2-diphenylethylenediamine.

Personal protective equipment (PPE): Wear chemical-resistant nitrile gloves, safety glasses or goggles, and a laboratory coat. Work in a well-ventilated fume hood, especially when weighing powder, to avoid inhalation of fine particles or dust.

Storage: Store in a tightly sealed container in a cool, dry, well-ventilated area away from strong acids, oxidizers, and moisture. Recommended storage temperature is typically 2–8 °C or room temperature as specified on the product label and CoA. Keep away from incompatible materials.

Waste disposal: Dispose of waste in accordance with local, regional, and national regulations for amine-containing chemical waste. Do not pour down the drain without prior neutralization and regulatory clearance.

Preparation and Quality Considerations

meso-1,2-Diphenylethylenediamine is classically obtained by the reduction of the corresponding dioxime (benzil dioxime) or by diastereoselective reduction of 2-amino-1,2-diphenylethanone derivatives. The meso diastereomer is typically isolated and purified by recrystallization from appropriate solvents to achieve the required diastereomeric purity.

Purity and specification: For sensitive asymmetric catalysis applications, diastereomeric purity is critical. Researchers should request the certificate of analysis (CoA) to confirm purity by HPLC or GC, melting point, and optical rotation (which should be zero or near-zero for the pure meso form, distinguishing it from the chiral (R,R) and (S,S) enantiomers).

Lot-to-lot consistency: When scaling reactions or comparing results across experiments, ensure reagent lot consistency. Contact Aladdin Scientific technical support if diastereomeric purity data are required beyond what is stated on the standard CoA.

Frequently asked questions

What is the difference between meso-1,2-diphenylethylenediamine and the (R,R) or (S,S) enantiomers?

The meso form has one R and one S stereocenter, giving an internal plane of symmetry so the molecule is achiral and optically inactive (zero optical rotation). The (R,R) and (S,S) forms are chiral, optically active enantiomers with equal but opposite optical rotations. In ligand design, the choice of diastereomer dictates the stereochemical outcome of the resulting metal complex or catalyst.

Which solvents are recommended for dissolving meso-1,2-diphenylethylenediamine?

The compound is generally soluble in polar organic solvents such as methanol, ethanol, dichloromethane, and dimethylformamide (DMF). Solubility in water is limited due to the hydrophobic phenyl groups. Always confirm solubility in your specific solvent system with a small-scale test before use in sensitive applications.

How should I confirm the diastereomeric purity of the meso form before use?

The most straightforward approach is to check the optical rotation: pure meso-1,2-diphenylethylenediamine should show an optical rotation of approximately zero. Chiral HPLC can also resolve the three diastereomers (meso, R,R, and S,S) and provide quantitative purity data. Request the Aladdin CoA for lot-specific analytical data.

Is meso-1,2-diphenylethylenediamine suitable for use as a chiral inducer in asymmetric reactions?

Because the meso form is achiral, it cannot directly serve as a chiral inducer on its own. However, it is frequently used as a precursor to synthesize unsymmetrical chiral ligands by selective mono-functionalization with a chiral partner, or as a reference compound and building block in ligand libraries. For direct chiral induction, the (R,R) or (S,S) enantiomers are typically preferred.

References

1. Jacobsen, E. N.; Zhang, W.; Muci, A. R.; Ecker, J. R.; Deng, L. Highly enantioselective epoxidation catalysts derived from 1,2-diaminocyclohexane. J. Am. Chem. Soc. 1991, 113, 7063–7064. (Background reference for salen-diamine ligand context; specific applicability to diphenyl variant requires verification.) doi:10.1021/ja00018a068
2. Sigma-Aldrich product listing 458511 for meso-1,2-Diphenylethylenediamine. (Cross-reference cited in source material; full specification details to be confirmed from current supplier CoA.)

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.