Structural chemistry phosphates

While the scheme is attractive and in practice of some predictive value, the structural chemistry of the oxomolybdate-phosphonate/organoimine-copper system is significantly more complex than the naive model suggests. Consequently, a variety of molybdophosphate subunits are encountered, depending on crystallization conditions and the nature of the phosphate components, as well as diverse linkage modes of the Cu(II) sites to the molybdophosphate subunits. 

Flanigen s review describes the structures, chemistry, and potential applications of alumino-phosphate molecular sieves (ALPO4-S) [41]. There are many ALPO4 structures with a wide variety of pore sizes and shapes. The Al/P ratio in the ALPO4 framework is always 1. All ALPO4-S are therefore neutral, have no ion-exchai e capacity, and cannot be made acidic. This excludes acid catalytic applications except where the acid sites should be extremely weak. Olefin isomerization, certain aromatic alkylations, and MTO are potential applications [42]. 

Such important technological and ecological problems can be solved successfully only using fundamental knowledge on structural chemistry of actinide compounds and, in particular, phosphates. For this purpose, use of modem instmmental methods of investigation of solids is needed. 

The successful development of structural chemistry of actinide phosphates will rely in many respects on experimental results obtained Ifom the chemical and structural research of analogous lanthanide compounds. Lanthanide phosphates have many more known structure modifications [10, 11]. 

The oxygen chemistry of pentavalent antimony was formerly very perplexing, and many compounds-some anhydrous, some hydrated-were described as ortho-, meta-, and pyro-antimonates and were assigned formulae analogous to those of phosphates. As a result of the study of the structures of many of these crystalline compounds it is found that their structural chemistry is very simple and quite different from that of phosphates, arsenates, and vanadates, being based not on tetrahedral but on octahedral coordination of Sb by oxygen. Many of the old formulae require revision. The compounds in question fall into two main groups ... 

Nanoporous materials with channels and cavities of molecular dimensions have a number of potential applications, for example, in catalysis, ion-exchange, gas adsorption, etc. Of the amine-templated transition-metal phosphates, the zinc phosphates have the richest structural chemistry and show a variety of materials with different structural dimensionality. Jensen and coworkers [222] prepared amine-templated zinc phosphates that are an interesting example of the correlation between the temperature for the synthesis and die density/structural dimensionality of the synthetic products that may be obtained. 

E. Thilo, The structural chemistry of condensed inorganic phosphates, Agnew. Chem. Int. Ed. Engl.) 4, 1061 (1965). 

FIGURE 5.35 Crystal structures of phosphate esters, (a) (C Hj CHjOljPfOlOH, (b) (CgHjO) , (c) (p-ClCgH50)2P(0)0H. (Adapted from D.E.C. Corbridge, The structural chemistry of phosphorous compounds. Topics Phos. Chem., 3, 57, 1966 S. Ohashi, Chromatography of the phosphorus oxyacids. Pure Appl. Chem., 44, 415, 1975 US 3,634,262.)... 

Orthophosphazate anions are capable of linking together through shared nitrogen atoms (7.20) and (7.21), and limited studies to date indicate a potential structural chemistry of phosphazates, analogous to that of the condensed phosphates (7.19) (Chapter 5.3). 

Although the structural chemistry of molybdenum and vanadium phosphates is very diverse these compounds seem to be prototypes for open framework transition and main group metal phosphates. Recent results have shown that zeolite-like compounds like zinc/cobalt phosphates [731, indium phosphates [74], nickel/aluminum phosphates [75], cobalt/boron phosphates [76], manganese and cobalt phosphonates with giant 44-membered rings forming ellipsoidal cavities [77] can be synthesized. All these examples show that the diverse chemistry of octahedral-tetrahedral framework structures is a vast field where... 

There are many common features to the structural chemistry of rare earth compounds formed by the tetrahedral oxoanions RXO4, where X is a pentavalent element (P, As, V, Cr). Nevertheless, considerably less structural and other information is available for the rare earth arsenates than for the phosphates and vanadates. 

Closely related to the carboxylic acids and nitriles discussed in the previous chapter are the carboxylic acid derivatives, compounds in which an acyl group is bonded to an electronegative atom or substituent that can net as a leaving group in a substitution reaction. Many kinds of acid derivatives are known, but we ll be concerned primarily with four of the more common ones acid halides, acid anhydrides, esters, and amides. Esters and amides are common in both laboratory and biological chemistry, while acid halides and acid anhydrides are used only in the laboratory. Thioesters and acyl phosphates are encountered primarily in biological chemistry. Note the structural similarity between acid anhydrides and acy) phosphates. 

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