1,2-Bis(diphenylphosphino)ethane

1,2-Bis(diphenylphosphino)ethane (dppe) is an organophosphorus compound with the formula (Ph2PCH2)2 (Ph = phenyl). It is a commonly used bidentate ligand in coordination chemistry. It is a white solid that is soluble in organic solvents.

1,2-Bis(diphenylphosphino)ethane
Names
IUPAC name
Ethane-1,2-diylbis(diphenylphosphane)
Other names
1,2-Bis(diphenylphosphino)ethane
Diphos
Dppe
Identifiers
3D model (JSmol)
761261
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.015.246
EC Number
  • 216-769-2
9052
UNII
Properties
C26H24P2
Molar mass 398.42 g/mol
Melting point 140 to 142 °C (284 to 288 °F; 413 to 415 K)
Hazards
GHS pictograms
GHS Signal word Warning
H302, H315, H319, H332, H335, H400, H410
P261, P264, P270, P271, P273, P280, P301+312, P302+352, P304+312, P304+340, P305+351+338, P312, P321, P330, P332+313, P337+313, P362, P391, P403+233, P405, P501
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

Preparation

The preparation of dppe is by the alkylation of NaPPh2:[1][2]

P(C6H5)3 + 2 Na → NaP(C6H5)2 + NaC6H5

NaP(C6H5)2, which is readily air-oxidized, is treated with 1,2-dichloroethane (ClCH2CH2Cl) to give dppe:

2 NaP(C6H5)2 + ClCH2CH2Cl → (C6H5)2PCH2CH2P(C6H5)2 + 2 NaCl

Reactions

The reduction of dppe by lithium to give PhHP(CH2)2PHPh has been reported.[3]

Ph2P(CH2)2PPh2 + 4 Li → PhLiP(CH2)2PLiPh + 2 PhLi

Hydrolysis gives the bis(secondary phosphine):

PhLiP(CH2)2PLiPh + 2 PhLi + 4H2O → PhHP(CH2)2PHPh + 4 LiOH + 2 C6H6
The bis(dppe) complex HFeCl(dppe)2 is one of the most accessible transition metal hydrides.

Treatment of dppe with conventional oxidants such as hydrogen peroxide (H2O2), aqueous bromine (Br2), etc., produces dppeO in low yield (e.g., 13%) as a result of non-selective oxidation.[4] Selective mono-oxidation of dppe can be achieved by reaction with PhCH2Br to give dppeO.

Ph2P(CH2)2PPh2 + PhCH2Br → Ph2P(CH2)2PPh2(CH2Ph)+Br−

 

 

 

 

(2.3.)

Ph2P(CH2)2PPh2(CH2Ph)+Br− + NaOH + H2O → Ph2P(CH2)2P(O)Ph2

 

 

 

 

(2.4.)

Hydrogenation of dppe gives the ligand bis(dicyclohexylphosphino)ethane.

Coordination complexes

Many coordination complexes of dppe are known, and some are used as homogeneous catalysts. Dppe is almost invariably chelating, although there are examples of monodentate (e.g., W(CO)5(dppe)) and of bridging behavior.[5] The natural bite angle is 86°.[6]

References
  1. W. Hewertson and H. R. Watson (1962). "283. The preparation of di- and tri-tertiary phosphines". J. Chem. Soc.: 1490–1494. doi:10.1039/JR9620001490.
  2. Girolami, G.; Rauchfuss, T.; Angelici, R. Synthesis and Technique in Inorganic Chemistry, 3rd ed.; University Science Books: Sausalito, CA, 1999; pp. 85-92. ISBN 0-935702-48-2
  3. Dogan, J.; Schulte, J.B.; Swiegers, G.F.; Wild, S.B. (2000). "Mechanism of Phosphorus-Carbon Bond Cleavage by Lithium in Tertiary Phosphines. An Optimized Synthesis of 1, 2-Bis (phenylphosphino) ethane". J. Org. Chem. 65 (4): 951–957. doi:10.1021/jo9907336. PMID 10814038.
  4. Encyclopedia of Reagents for Organic Synthesis 2001 John Wiley & Sons, Ltd
  5. Cotton, F.A.; Wilkinson, G. Advanced Inorganic Chemistry: A Comprehensive Text, 4th ed.; Wiley-Interscience Publications: New York, NY, 1980; p.246. ISBN 0-471-02775-8
  6. Birkholz (née Gensow), Mandy-Nicole; Freixa, Zoraida; van Leeuwen, Piet W. N. M. (2009). "Bite angle effects of diphosphines in C–C and C–X bond forming cross coupling reactions". Chemical Society Reviews. 38 (4): 1099. doi:10.1039/B806211K. PMID 19421583.
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