Synthesis and Solid-State Decomposition

These two topics are now combined, as many thermal decomposition reactions in chromium chemistry are useful synthetic routes. Table 6.14 provides a list of complexes that could have potential in kinetic or photochemical studies. It has long been known that addition of NH4X salts to [Cr(en)3]X3 systems frequently lowers the temperature at which en is lost (the steric course of the reaction may also be altered). The thermal decomposition of [Cr(en)3]P04 is assisted by added 

Li[Cr(edtp)]-4H20 edtp = ethylenediaminetetra-3-propionate synthesis and resolution 151 

A particularly useful synthetic route is the solid-state dehydration-anation process (I5) 37.i38) ambidentate ligands, then bridging dinuclear 

A new route to the synthesis of [CrCl3(thf)3], an important starting material in the synthesis of Cr(III) amine complexes, is described. CrCl3 6H20 is dehydrated in refluxing SOCI2 and thf added directly to the reaction mixture. The violet product is quite stable in the open air for several hours.  

A series of Cr(III) complexes with edta-like ligands, viz edtp (16) (5)-pdtp (17) and (5,S)-cydtp (18), have been prepared. Three isomeric forms of 

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This phase seems to be predominating in Zi, the sample obtained by solid state decomposition in presence of urea. This sample could have additional porosity, due to loss of CO2 during synthesis of and/or calcination. This could possibly result in exposure of additional catalytically active centers, making it highly active catalyst. The data in Table 1 illustrates the relative catalytic activity of various zinc oxide towards decomposition of propan-2-ol at 653"K at a contact time of 1.6 seconds. Under the above conditions all the catalyst showed dehydrogenation activity only the reactivity following the order Zi>Z2 4 Z5>Z3. 

One of the major uses of DTA has been to follow solid-state reactions as they occur. All decomposition reactions (loss of hydrates, water of constitution, decomposition of inorganic anions, e.g.- carbonate to carbon dioxide gas, etc.) are endothermic and irreversible. Likewise are the synthesis reactions such as... 

Scheme 6.1. Synthesis of ternary single-source precursors and decomposition to solid state materials.

Decomposition of the organics leads then to the separation of all elements into Cu and Y oxides and barium carbonate. This brings the synthesis parameters back to the problems encountered in the conventional solid state approach except that the heterogeneity may be over a submicron scale. Thus, reaction temperature may be slightly lowered (850°C instead of 900°C). 

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