Diphenyl diselenide

Diphenyl diselenide

Chemical structure of diphenyl diselenide
Space-filling model
Names
IUPAC name Diphenyl diselenide
Other names Phenyl diselenide
Identifiers
CAS Number	1666-13-3 Y
ChemSpider	14710 Y
Jmol 3D model	Interactive image
PubChem	15460
RTECS number	JM9152500
InChI InChI=1S/C12H10Se2/c1-3-7-11(8-4-1)13-14-12-9-5-2-6-10-12/h1-10H Y Key: YWWZCHLUQSHMCL-UHFFFAOYSA-N Y InChI=1/C12H10Se2/c1-3-7-11(8-4-1)13-14-12-9-5-2-6-10-12/h1-10H Key: YWWZCHLUQSHMCL-UHFFFAOYAK
SMILES c1ccc(cc1)[Se][Se]c2ccccc2
Properties
Chemical formula	C12H10Se2
Molar mass	312.15 g·mol−1
Appearance	Orange powder
Density	1.84 g/cm3
Melting point	59 to 61 °C (138 to 142 °F; 332 to 334 K)
Solubility in water	Insoluble
Solubility in other solvents	Dichloromethane
Structure
Coordination geometry	90° at Se C2 symmetry
Dipole moment	0 D
Vapor pressure	{{{value}}}
Related compounds
Related compounds	Ph2S2, C6H5SeH
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Diphenyl diselenide is the chemical compound with the formula (C₆H₅)₂Se₂, abbreviated Ph₂Se₂ This orange-coloured solid is the oxidized derivative of benzeneselenol. It is used as a source of the PhSe unit in organic synthesis.

Ph₂Se₂ is prepared by the oxidation of benzeneselenoate, the conjugate base of benzeneselenol which is generated via the Grignard reagent:

PhMgBr + Se → PhSeMgBr

2 PhSeMgBr + Br₂ → Ph₂Se₂ + 2 MgBr₂

The molecule has idealized C₂-symmetry, like hydrogen peroxide and related molecules. The Se-Se bond length of 2.29 Å the C-Se-Se-C dihedral angle is 82° and the C-Se-Se angles are near 110°.

Reactions

One reactions characteristic of Ph₂Se₂ is its reduction:

Ph₂Se₂ + 2 Na → 2 PhSeNa

PhSeNa is a useful nucleophile used to introduce the phenylselenyl group by nucleophilic substitution of alkyl halides, alkyl sulfonates (mesylates or tosylates) and epoxides. The example below was taken from a synthesis of morphine.

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Another characteristic reaction is chlorination:

Ph₂Se₂ + Cl₂ → 2 PhSeCl

PhSeCl is a powerful electrophile, used to introduce PhSe groups by reaction with a variety of nucleophiles, including enolates, enol silyl ethers, Grignard reagents, organolithium reagents, alkenes and amines. In the sequence below (early steps in the synthesis of Strychnofoline), a PhSe group is introduced by reaction of a lactam enolate with PhSeCl. This sequence is a powerful method for the conversion of carbonyl compounds to their α,β-unsaturated analogs.

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Diphenyl diselenide itself is also a source of a weakly electrophilic PhSe group in reactions with relatively powerful nucleophiles like Grignard reagents, lithium reagents and ester enolates (but not ketone enolates or weaker nucleophiles). PhSeCl is both more reactive, and more efficient, since with Ph₂Se₂ half of the selenium is wasted.

Ph₂Se₂ + Nu⁻ → PhSeNu + PhSe⁻

N-Phenylselenophtalimide (N-PSP) can be used if PhSeCl is too strong and diphenyl diselenide is too weak or wasteful.