Vanadium phosphonate structure, layere

Zinc [37], manganese [38], molybdenum [34], and vanadium [40,41] also form lamellar structures. For example, molybdenyl phenylphosphonate forms a linear structure with double chains in which the molybdenyl oxygens of the adjacent chains point toward each other and the phenyl groups are on the outside [42], As is the case with zirconium phosphate and phosphonate, the layered nature of the above metal phosphonates is similar to that of the respective phosphates. Among these, vanadium phosphonates have generated greater interest in view of their importance as industrial catalysts. 

Using this approach leads to replace phosphates by other chelating agents. The first attempts concerned phosphonates and were developed by Alberti and Clearfield ([76] and Refs therein) in the early seventies. These authors showed that phosphonates could replace phosphates in a lot of syntheses, but this way was essentially devoted to layered compounds in order to increase the distance between the layers, and not with the aim of obtaining porous compounds. They mainly used monophosphonates, but some further attempts with diphosphonates or functionalized monophosphonates lead to pillared compounds which sometimes offer frameworks with an open structure. Using this way, we recently characterized [77] a porous vanadium(IV) diphosphonate (NH4)2(H20)2(V0) (V0(H20))2 (03P—CH2—P03)2 or MIL-2 (for Materials of Institut Lavoisier) in which the channels are occupied with water molecules and ammonium ions (Fig. 15 (left)). 

Lamellar or linear structures are also formed by various other metal ions, such as zinc, (268) manganese, (269) molybdenum, (270) and vanadium (271,272). Among these other solids, vanadium derivatives attracted significant attention due to their potential as industrial catalysts. The structures of the metal phospho-nates are similar to those of the corresponding phosphates, in a manner similar to the zirconium phosphate/phosphonates. Polymerization of phenylphosphonate, for example, with Mo(IV) resulted in a linear double-stranded structure where the phenyl groups are positioned on the outside of the linear structure (273). These othCT metal derivatives are bound to yield many future investigations regarding the fundamental and applied chemistry of layered mataials. 

---