Diphosphines

Diphosphines are a class of compounds used as ligands in inorganic and organometallic chemistry. They are identified by the presence of two phosphine ligands joined by a backbone, and are usually chelating.

Additional recommended knowledge

Daily Visual Balance Check

What is the Correct Way to Check Repeatability in Balances?

How to ensure accurate weighing results every day?

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 Bu₂^tP(CH₂)₁₀PBu₂^t can give complexes that have as many as 72 atoms in a ring ^[2].

Common ligands

While there can be very many diphosphine ligands possible, there are some which are commonly used, and which are commercially available. These include:

• 1,1-Bis(diphenylphosphino)methane ("dppm")
• 1,2-Bis(diphenylphosphino)ethane ("dppe")
• 1,3-Bis(diphenylphosphino)propane ("dppp")
• 1,1'-Bis(diphenylphosphino)ferrocene ("dppf")

References

1. ^ Wilkinson, G.; Gillard, R.; McCleverty, J. Comprehensive Coordination Chemistry: The synthesis, reactions, properties & applications of coordination compounds, vol.2.; Pergamon Press: Oxford, UK, 1987; p. 993. ISBN 0-08-035945-0
2. ^ 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