Alkoxy and Aryloxy Diphosphines

The structural formulae of the symmetrical derivatives (6.731a) can be compared with those of diphosphines (6.731b), diphosphine oxides (6.731c) and hypophosphoric esters (6.731d). 

Tetraalkoxy diphosphines (6.731a) or l,T-dialkyl 2,2 -dialkoxy diphosphines can be prepared from dialkoxyphosphines, and unsymmetrical dialkoxy diphosphines can also be prepared from the latter (6.732). 

The oxidation of tetra alkoxydiphosphines can yield pyrophosphites, isohypo-phosphites or pyrophosphates. With dimethyl sulphoxide, the proportions used determine the product (6.733). With acyl halides, P-C bonds are formed in a reaction which can be represented approximately as (6.734). 

The oxidation of 1,T dialkyl 2,2 dialkoxy diphosphines can give rise to three possible isomers. Examples of each of these are known, but they have different orders of stability and the simple 

The first isomer can be prepared from sodium dialkyl phosphinite and a dialkylphosphorochlori-dite at -78°C. Isomers of this type are usually very unstable and will easily oxidise or hydrolyse. The second type of isomer can be obtained from a dialkylphosphine oxide and a phosphorochloridite 

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