1,2-Bisethane (dppe) is a commonly used bidentate ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

 in coordination chemistry. Dppe is almost invariably chelated
Chelation is the formation or presence of two or more separate coordinate bonds between apolydentate ligand and a single central atom....

, although there are examples of unidentate (e.g., W(CO)5(dppe)) and of bridging behavior.


The preparation of dppe is conducted via the alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...

 of NaPPh2 which is typically prepared from triphenylphosphine
Triphenylphosphine is a common organophosphorus compound with the formula P3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature...

 (P(C6H5)3) as follows:
1. P(C6H5)3 + 2 Na → NaP(C6H5)2 + NaC6H5

NaP(C6H5)2, which is readily air-oxidized, is treated with 1,2-dichloroethane
The chemical compound 1,2-dichloroethane, commonly known by its old name of ethylene dichloride , is a chlorinated hydrocarbon, mainly used to produce vinyl chloride monomer , the major precursor for PVC production. It is a colourless liquid with a chloroform-like odour...

 (ClCH2CH2Cl) to give dppe:
2. 2 NaP(C6H5)2 + ClCH2CH2Cl → (C6H5)2PCH2CH2P(C6H5)2 + 2 NaCl


The reduction of dppe by lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...

 to give PhHP(CH2)2PHPh has been reported.
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


Treatment of dppe with conventional oxidants such as hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

 (H2O2), aqueous bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...

(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. 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 chemistry

Coordination complexes of dppe, and diphosphine ligands in general, are almost entirely used as homogeneous catalysts for a wide range of reactions. 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.
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