Other metal phosphates

The water elimination reactions of Co3(P04)2 8 H20 [838], zirconium phosphate [839] and both acid and basic gallium phosphates [840] are too complicated to make kinetic studies of more than empirical value. The decomposition of the double salt, Na3NiP3O10 12 H20 has been shown [593] to obey a composite rate equation comprised of two processes, one purely chemical and the other involving diffusion control, for which E = 38 and 49 kJ mole-1, respectively. There has been a thermodynamic study of CeP04 vaporization [841]. Decomposition of metal phosphites [842] involves oxidation and anion reorganization. 

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Another diagnostic method for determining the effect of the nature of the catalyst on the mechanism is the observation of the stereoselectivity of elimination [68,121,132]. It has been found, using the reaction of threo- and erythro-3-deutero-2-butanol, that, in a series of salt catalysts, only the phosphates Ca3(P04)2, CaHP04, Ba3(P04)2 and A1P04 preferred the E2 mechanism while on other metal phosphates and all carbonates, the El mechanism predominated [ 132]. 

NaOH was involved in the synthesis. After systematic studies, W.Q. Pang and S.L. Qiu developed a general approach to growing large single crystals of zeolites and related microporous materials from fluorine ion synthesis systems. Later, J.L. Guth and W.Q. Pang expanded the fluoride source hydrothermal synthesis approach to the synthesis of micro-porous aluminophosphates and other metal phosphates. 

Synthesis of Microporous Aluminophosphates and other Metal Phosphates in the Presence of Fluoride Source... 

Aluminum phosphates are the most commonly used phosphates for polymerization catalyst supports because they can be made with the high porosity that is necessary for fragmentation. However, many other metal phosphates are also known and are used in other areas of catalysis. These materials are often quite acidic and can also serve as supports for chromium oxide. 

The structures of many other metal phosphates have been reported in which the metal is in mixed or non-tetrahedral conformation, but without much information on the porosity or thermal stability. The vanadyl phosphates reported by Schindler and Baur, for example, can be considered to be built up from planar V509(P04)4 units that share phosphate tetrahedra. These have the same topology as 4MRs, so that analogue structures that are similar to zeolite structures that are made up completely of 4MRs such as sodalite and Rho can be prepared. 

Reaction of metal oxides with ammonium phosphates, magnesium acid phosphates, aluminum acid phosphates, and other metal phosphates. 

In this chapter I focus on structural features of metal-nucleotide binding to enzymes and also on other metal-phosphate complexes with individual enzymes. The appropriate theoretical consideration for the NMR and EPR experiments is discussed in each section. The first problem, which has been addressed for several different enzymes, is whether enzymes have a preference for certain stereoisomers of metal-nucleotides. This is fundamentally a structural problem and can be answered by preparation of individual stereoisomers, followed by binding and kinetic studies to detect the preference of an enzyme for one isomer over another. Qeland (1982) has compiled a list of current studies dealing with this question. Other complementary structural problems that can be addressed through the use of these nucleotide complexes is to use them to map distances between the nucleotide site and other substrate or metal-ion sites on enzymes. This is possible because Cr(lll) complexes are paramagnetic, whereas Co(lII) complexes are diamagnetic. Both types of complexes can be used for distance determinations, and each appUcation is discussed. 

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