Square-pyramidal coordination, vanadium oxide compounds

Spectra of octahedral vanadium(V) oxide compounds are presented in Figure 2. Undistorted vanadium(V) oxide compounds do not exist, and all vanadia octahedra are highly distorted, which give rise to short V-0 bonds. This is reflected in the Raman band position for the distorted octahedral vanadium oxide compounds which always occur in the 900-1000 cm region. The vanadia structure in 2 5 approaches a square-pyramidal coordination and the individual vanadia are linked... 

All of the above compounds are oxides. The application of the fluorine route already described for AlPOs and GaPOs has shown that it is also possible to obtain open framework structures with fluoride in the VPOs. This led to the discovery by Riou and Ferey [72] of the first open-framework fluorovanado(V)phosphate, ULM-7 or (H3N(CH2-CH2)NH3)[(V 02)2(P04)F], in which the building units are V2P trimers. Vanadium exhibits both octahedral and square pyramidal coordination, and fluoride ion is shared between them. The three-dimensional network generated by comer-sharing of these trimers, exhibits 10-membered rings occupied by diprotonated amines. 

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