Phosphorus oxides crystal structure

The selective oxidation of ra-butane to give maleic anhydride (MA) catalyzed by vanadium phosphorus oxides is an important commercial process (99). MA is subsequently used in catalytic processes to make tetrahydrofurans and agricultural chemicals. The active phase in the selective butane oxidation catalyst is identified as vanadyl pyrophosphate, (V0)2P207, referred to as VPO. The three-dimensional structure of orthorhombic VPO, consisting of vanadyl octahedra and phosphate tetrahedra, is shown in Fig. 17, with a= 1.6594 nm, b = 0.776 nm, and c = 0.958 nm (100), with (010) as the active plane (99). Conventional crystallographic notations of round brackets (), and triangular point brackets (), are used to denote a crystal plane and crystallographic directions in the VPO structure, respectively. The latter refers to symmetrically equivalent directions present in a crystal. 

With the exception of P4O10, efficiency values between 0.61 and 0.65 have been obtained. This indicates that, in spite of the differences among the crystal structures of the phosphorus oxides and oxide sulfides, their space-fillings are very similar. 

Figure 20 Crystal structures of various ternary and quaternary phosphide oxides of the alkaline earth, rare earth, and actinoid metals. Alkaline earth (rare earth, actinoid), transition metal, phosphorus, and oxygen atoms are drawn as large light grey, medium grey, filled, and open circles, respectively. Some relevant coordination polyhedra around the oxygen atoms and the transition metal-phosphorus bonds are emphasized...

The crystal structure of the hydroxyphosphorane (88) prepared by N2O4 oxidation of (87) showed an almost perfect tbp structure with the unit cell containing two molecules of the same helicity connected by H-bonds between the P-OH and carbonyl groups.The phosphorus ester (89), fashioned from two n-butyl tartrate moieties exists in solution due to intramolecular hydrogen bonds. On treatment with triethylamine, however, it forms the triethylammo-nium salt (90) of the corresponding hydroxyphosphorane. The pKa value of (89) was determined to be 7.7 in DMF and 4.4 in DMSO, similar to values for dichloroacetic acid in the same two solvents. ... 

These complexes were fully characterized and the X-ray crystal structure of 89 was also reported. The reactivity of these dinuclear complexes toward a variety of nitrogen- and phosphorus-donor ligands was described (104-106) as well as oxidative-addition reaction with iodine (104). 

The aluminophosphate molecular sieves (AiP04 s) consist of aluminum and phosphorus linked by oxide ions. In the larger family of aluminophosphate based molecular sieves with three or more framework cations an additional 13 elements have been incorporated with a variety of crystal structures. The whole aluminophosphate based molecular sieve family comprises more than two dozen crystal structures and about two hundred compositions. While AIPO4 molecular sieves with only two framework elements are catalytically inactive, most of the three or multi-component aluminophosphate based molecular sieves possess cation exchange capacity, and in the protic form they display carboniogenic catalytic activity. 

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