Diphosphines, sometimes called bisphosphanes, are

organophosphorus compound Organophosphorus compounds are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective in ...

s most commonly used as bidentate

phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...

s in

inorganic In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

and

organometallic chemistry Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

. They are identified by the presence of two phosphino groups linked by a backbone, and are usually

chelating Chelation is a type of bonding of ions and molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a Denticity, polydentate (multiple bonded) ligand and a single central metal atom. These l ...

. A wide variety of diphosphines have been synthesized with different linkers and R-groups. Alteration of the linker and R-groups alters the electronic and steric properties of the ligands which can result in different coordination geometries and catalytic behavior in homogeneous catalysts.

Synthesis

222px, Chlorodiisopropylphosphine is a popular building block for the preparation of diphosphines.

From phosphide building blocks

Many widely used diphosphine ligands have the general formula Ar₂P(CH₂)_nPAr₂. These compounds can be prepared from the reaction of X(CH₂)_nX (X=halogen) and MPPh₂ (M = alkali metal): :Cl(CH₂)_nCl + 2 NaPPh₂ → Ph₂P(CH₂)_nPPh₂ + 2 NaCl Diphosphine ligands can also be prepared from dilithiated reagents and chlorophosphines: :XLi₂ + 2 ClPAr₂ → X(PAr₂)₂ + 2 LiCl (X = hydrocarbon backbone) This approach is suitable for installing two dialkylphosphino groups, using reagents such as

chlorodiisopropylphosphine Chlorodiisopropylphosphine is an organophosphorus compound with the formula CH3)2CHPCl. It is a colorless liquid that reacts with water and oxygen. The compound is used to prepare tertiary phosphines and phosphinite ligands. Synthesis and re ...

. Another popular method, suitable for preparing unsymmetrical diphosphines, involves the addition of secondary phosphines to vinylphosphines: :Ph₂PH + 2 CH₂=CHPAr₂ → Ph₂PCH₂-CH₂PAr₂ (2-Lithiophenyl)diphenylphosphine can be used also to give unsymmetrical diphosphines. The lithiated reagent is available from (2-bromophenyl)diphenylphosphine: :Ph₂P(C₆H₄Br) + BuLi → Ph₂P(C₆H₄Li) + BuBr :Ph₂P(C₆H₄Li) + R₂PCli → Ph₂P(C₆H₄PR₂) + LiCl

From bis(dichlorophosphine) precursors

Many diphosphines are prepared from compounds of the type X(PCl₂)₂ where X = (CH₂)_n or C₆H₄. The key reagents are

1,2-bis(dichlorophosphino)ethane 1,2-Bis(dichlorophosphino)ethane is an organophosphorus compound with the formula (CH2PCl2)2. A colorless liquid, it is a precursor to chelating diphosphines. Synthesis and reactions It is prepared by the reaction of ethylene, white phosphorus, a ...

and 1,2-bis(dichlorophosphino)benzene. 164px, 1,2-Bis(dichlorophosphino)ethane is a key intermediate in the synthesis of 1,2-bis(dimethylphosphino)ethane.

Chain length and coordinating properties

The short-chain diphosphine

dppm 1,1-Bis(diphenylphosphino)methane (dppm), is an organophosphorus compound with the formula CH2(PPh2)2. Dppm, a white, crystalline powder, is used in inorganic and organometallic chemistry as a ligand. It is more specifically a chelating ligand be ...

tends to promote metal-metal interactions as illustrated by

A-frame complex In organometallic chemistry, A-frame complexes are coordination compounds that contain two bridging bidentate ligands and a single atom bridge. They have the formula , where ''bd'' is a bidentate ligand like dppm, and X and L are a wide variet ...

es. When the two phosphine substituents are linked by two to four carbon centres, the resulting ligands often chelate rings with a single metal. A common diphosphine ligand is

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

, which forms a five-membered chelate ring with most metals. Some diphosphines, such as the extraordinary case of ^''t''Bu₂P(CH₂)₁₀P^''t''Bu₂, give macrocyclic complexes with as many as 72 atoms in a ring.Cotton, F.A.; Wilkinson, G. ''Advanced Inorganic Chemistry: A Comprehensive Text'', 4th ed.; Wiley-Interscience Publications: New York, NY, 1980; p.246. To position phosphine donor groups trans on a coordination sphere, several atoms are required to link the donor centres and long-chain diphosphines are typically floppy and do not chelate well. This challenge has been resolved by the long but rigid diphosphine SPANphos. The bite angle of the diphosphine influences the reactivity of the metal center. Some examples of non-chelating diphosphine also exist. Due to steric effect, these phosphorus atoms can not react with anything except a proton. It can be changed from non-chelating to chelating diphosphine by tuning the length of the linking arm.

Representative ligands

Particularly common diphosphine ligands are shown in the table below:http://old.iupac.org/reports/provisional/abstract04/RB-prs310804/TableVII-3.04.pdf {, class="sortable wikitable" style="background-color:#ffffff;" !Abbreviation !Common name
(from which abbreviation derived) !Structure !Bite Angle , - , dppm ,

1,1-Bis(diphenylphosphino)methane 1,1-Bis(diphenylphosphino)methane (dppm), is an organophosphorus compound with the formula CH2(PPh2)2. Dppm, a white, crystalline powder, is used in inorganic and organometallic chemistry as a ligand. It is more specifically a chelating ligand beca ...

, 73 , - , dmpe ,

1,2-Bis(dimethylphosphino)ethane 1,2-Bis(dimethylphosphino)ethane (dmpe) is a diphosphine ligand in coordination chemistry. It is a colorless, air-sensitive liquid that is soluble in organic solvents. With the formula (CHPMe), dmpe is used as a compact strongly basic spectator l ...

, , - , dippe , 1,2-Bis(diisopropylphosphino)ethane ,

1,2-Bis(diisopropylphosphino)ethane-2D-by-AHRLS-2012

, , - , dppbz , 1,2-Bis(diphenylphosphino)benzene , , , - , dppe ,

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

, , 86 , - ,

DIPAMP DIPAMP is an organophosphorus compound that is used as a ligand in homogeneous catalysis. It is a white solid that dissolves in organic solvents. Work on this compound by W. S. Knowles was recognized with the Nobel Prize in Chemistry. DIPAMP w ...

, derivative of phenylanisylmethylphosphine , , , - , dcpe ,

Bis(dicyclohexylphosphino)ethane Bis(dicyclohexylphosphino)ethane, abbreviated dcpe, is an organophosphorus compound with the formula (C6H11)2PCH2CH2P(C6H11)2. It is a white solid that is soluble in nonpolar organic solvents. The compound is used as a bulky and highly basic dip ...

, , , - , dppp ,

1,3-Bis(diphenylphosphino)propane 1,3-Bis(diphenylphosphino)propane (dppp) is an organophosphorus compound with the formula PhP(CH)PPh. The compound is a white solid that is soluble in organic solvents. It is slightly air-sensitive, degrading in air to the phosphine oxide. It i ...

, , 91 , - , dppb , 1,4-Bis(diphenylphosphino)butane , , 94 , - ,

DIOP Diop (Wolof: ), uncommonly spelled Dioup, is a popular Wolof surname in Senegal and Gambia (where it is commonly written "Jobe"), and may refer to: * Aïda Diop (born 1970), Senegalese sprinter * Alice Diop (born 1979) Documentary film-maker in Fr ...

, (S,S)-DIOP (O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane) , , , - ,

Chiraphos Chiraphos is a chiral diphosphine employed as a ligand in organometallic chemistry. This bidentate ligand chelates metals via the two phosphine groups. Its name is derived from its description — being both ''chiral'' and a ''phosphine''. As ...

, 2,3-Bis(diphenylphosphino)butane , , , - , BINAP , 2,2'-Bis(diphenylphosphino)-1,1'-binaphthyl , , 93 , - , Xantphos , 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene , , 108 , - ,

DPEphos Bis 2-diphenylphosphino)phenylether, also known as DPEphos, is a wide bite angle diphosphines, diphosphine ligand used in Inorganic chemistry, inorganic and organometallic chemistry. The name DPEphos is derived from diphenyl ether (DPE) which ...

, Bis 2-diphenylphosphino)phenylether , , 104 , - , SPANphos , 4,4,4',4',6,6'-Hexamethyl-2,2'-spirobichromane-8,8'-diylbis(diphenylphosphane) , , , - ,

SEGPHOS SEGPHOS is a chiral ligand developed by Takasago that is used in asymmetric synthesis. It was developed after BINAP BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) is an organophosphorus compound. This chiral diphosphine ligand ...

, 4,4'-Bi-1,3-benzodioxole-5,5'-diylbis(diphenylphosphane) , , , - , dppf , 1,1'-Bis(diphenylphosphino)ferrocene , , 99 , - , Me-DuPhos , 1,2-Bis(2,5-dimethylphospholano)benzene , , , - , Josiphos , (Diphenylphosphino)ferrocenyl-ethyldicyclohexylphosphine1,5-Diaza-3,7-diphosphacyclooctanes , ] , , - , P2N2 ,

1,5-Diaza-3,7-diphosphacyclooctanes 1,5-Diaza-3,7-diphosphacyclooctanes are organophosphorus compounds with the formula 'NCHP(R)CH often abbreviated PN. They are air-sensitive white solids that are soluble in organic solvents. The ligands exist as meso and d,l-diastereomers, but o ...

, ,

References

cs:Difosfan pl:Difosfina