Polydentate phosphines and macrocycles

Phosphines that contain another one or more phosphorus atoms are particularly useful as ligands for transition metals. This stems from the fact that they can form a stronger bond to the metal with both phosphorus atoms donating and hence placing substituents in a well-defined position. (This has been exploited very successfully in the case of chiral bidentate phosphines.) 

Similar procedures as described in the previous sections are still valid for the preparation of these compounds, but there are some specific synthetic methods which warrant attention. 

The synthesis of poly phosphine macrocycles requires the joining of a bidentate phosphine with other donor ligands via an alkyl or aryl chain. The synthesis of 

Coordinated secondary phosphines will also add vinyldiphenylphosphine to form terdentate ligands. 

Chiral phosphines can be divided into two main classes those which are chiral at phosphorus and those which have chiral substituents or planar/axial chirality. In addition, mono-, bi-, and tridentate phosphines have been prepared and used successfully. 

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