Multi-Ring and Cage Polyphosphines

The existence of many multi-ring and cage polyphosphines built from P-P bonds has now been established. In some cases the P-P frameworks are analogous to those of parent hydrides or phosphide anions (Chapters 4 and 8). 

Although some of the more complex polyphosphines have been made, their separation and isolation in pure form has not yet been achieved. Many are yellow or colourless liquids which are frequently difficult to crystallise. As the number of P atoms increases, the likelihood of structural isomers increases. 

In some cases the configuration adopted by a given P/R atomic ratio is governed by steric affects associated with the organic group R (6.708c,d, 6.708i,j). Typical methods used to produce these complex polyphosphines are indicated in 

The condensed cage compound P4(PPh)g, forms a phosphorus pentoxide-type (adamantane-type) structure (Table 4.12). It can be made in high yields by reaction (6.714) which is carried out at -80 C in ether in the absence of air. The product is a yellow solid, very soluble in benzene, tetrahydrofu-ran, dioxane and so on, but insoluble in water and n-hexane. It is not oxidised in dry air but above 60°C it softens and converts to higher polymeric materials. The oxy derivative, P4(PPh)504, is made by a reaction similar to (6.714) using POCI3 instead of PCI3. 

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