Phosphonate Polyoxometallates

Polyoxometallate structures in which RPOj groups replace the conventional PO4 tetrahedra have attracted much attention during recent years. Both finite clusters and highly polymerised structures have been studied with special attention being devoted to oxo-vanadium and oxo-molybdenum 

The V40gF(PhP03)4 and V70i2Cl(PhP03)6 anions are built from [VO5] square pyramida and [PhPOj] tetrahedra which share corners to produce roughly spherical cages of V-O-P bonds, with the halogen atoms situated at their centres. 

Many complex structures can be formed with various Mo and V oxoanions and organic cations. The crystalline compound [Me2NH2]K4VioOio(H20)2(OH)2(P04)7-4H20 contains a remarkable inorganic double helix consisting of two intertwined but independent spirals of linked O and V atoms [106]. 

The neutral complex [ BUPO3 AlBu has a compact inner network of Al-O-P bonds with the A1 and P atoms forming the corners of a cube, and the butyl groups pointing outwards. The latter forms an organic sheath and confers solubility in organic solvents (see Chapter 9). 

---