1,2-Bis(diphenylphosphino)ethane
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| 1,2-Bis(diphenylphosphino)ethane | |
|---|---|
 
| |
| Chemical name | 1,2-Bis(diphenylphosphino)ethane |
| Chemical formula | (C6H5)2PCH2CH2P(C6H5)2 |
| Molecular mass | 397.95 g/mol |
| Melting point | 140-142 °C |
| Disclaimer and references | |
1,2-Bis(diphenylphosphino)ethane (dppe) is a commonly used bidentate ligand in coordination chemistry. Dppe is almost invariably chelated, although there are examples of unidentate (e.g., W(CO)5(dppe)) and of bridging behavior.[1]
Preparation
The preparation of dppe is conducted via the alkylation of NaPPh2 which is typically prepared from triphenylphosphine (P(C6H5)3) as follows:[1]
- 1. 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 of dppe
Reduction
The reduction of dppe by lithium to give PhHP(CH2)2PHPh has been reported.[1]
- 1. Ph2P(CH2)2PPh2 + 4 Li → PhLiP(CH2)2PLiPh + 2 PhLi
Hydrolysis by water gives:
- 2. PhLiP(CH2)2PLiPh + 2 PhLi + 4H2O → PhHP(CH2)2PHPh + 4 LiOH + 2C6H6
Oxidation
Treatment of dppe with conventional oxidants such as hydrogen peroxide (H2O2), aqueous bromine (Br2), etc., always produces dppeO in low yield (e.g., 13%) as a result of non-selective oxidation leading to mixtures of the starting material, the monoxide, and dioxide.[1] Selective mono-oxidation of dppe can be achieved by reaction with PhCH2Br to give dppeO.
- 3. Ph2P(CH2)2PPh2 + PhCH2Br → Ph2P(CH2)2PPh2(CH2Ph)+Br-
This is followed by purification and alkaline catalyzed hydrolysis of the mono-phosphonium salt.
- 4. Ph2P(CH2)2PPh2(CH2Ph)+Br- + NaOH + H2O → Ph2P(CH2)2P(O)Ph2
Coordination complexes of dppe
Coordination complexes of dppe, and diphosphine ligands in general, are almost entirely used as homogeneous catalysts for a wide range of reactions. Chiral diphosphines are especially important to the pharmaceutical industry [1] for their ability to catalyze asymmetric reactions [1] Two simple coordination complexes of dppe include Pd(dppe)2 and Ir(dppe)2. Pd(dppe)2 can be prepared by reduction of Pd(II) with NaBH4. It is most conveniently prepared, however, in situ from Pd(OAc)2.[1]
dppe analogues
dppe is one compound of a larger class of ligands known as the diphosphines. The most widely used diphosphine ligands are the bis(diphenylphosphino)alkanes, Ph2P(CH2)nPPh2. These can be prepared from X(CH2)nX (X=halogen) and YPPh2 (Y=alkali metal) in THF [1]. Bidentate phosphines with only one bridging group such as dppm tend to promote metal-metal interaction or bond formation because the two donor P atoms are so close together. The use of chelate phosphines with many bridging groups giving long flexible chains has quite a different effect. For example, the chelate phosphine Bu2tP(CH2)10PBu2t can give complexes that have as many as 72 atoms in a ring [1].
dppv
Dppv is the acronym for 1,2-bis(diphenylphosphino)ethylene, (C6H5)2PCH=CHP(C6H5)2. Both cis (m.p. 125 °C) and trans (m.p. 126°C) isomers are known, being derived from the respective isomers of ClCH=CHCl. The substitution of chloride is stereospecific. The cis isomer, however, is almost exclusively used for applications of a ligand.
dmpe
| dmpe | |
|---|---|
| Chemical name | 1,2-bis(dimethylphosphino) ethane |
| Chemical formula | (CH3)2PCH2CH2P(CH3)2 |
| Molecular mass | 150.14 g/mol |
| CAS Number | 23936-60-9 |
| Boiling point | 180 °C |
| Flash point | 2 °F |
| Density | 0.9 g/mL at 25 °C |
| Disclaimer and references | |
Dmpe is prepared in a similar way to that of dppe.
- 1. (CH3)2P-P(CH3)2 + 2Na → 2NaP(CH3)2
- 2. 2NaP(CH3)2 + ClCH2CH2Cl → (CH3)2PCH2CH2P(CH3)2 + 2NaCl
Dmpe should be handled with care. It is toxic and exposure to the air may result in ignition.
Dppf
1,1'-Bis(diphenylphosphino)ferrocene (dppf) is also used as a ligand. As its name implies, its backbone is made up of a ferrocene moiety, as opposed to the ethylene backbone of dppe.
References
External links
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
