Decomposition of transition metal

Formation of fluoride-containing coordination compounds by decomposition of transition-metal tetrafluoroborates. J. Reedijk, Comments Inorg. Chem., 1982,1, 379-389 (34). 

The nucleation of these decomposition processes was studied by means of thermomicroscopy on single crystal cleavage plates of calcite, magnesite, dolomite and smithsonite (Fig. 59). The shape of the nuclei was found to be different for these carbonates, which might be also of importance for the decomposition mechanism. The partial pressure of water vapor has a pronounced effect on the decomposition of transition metal carbonates such as ZnC03 and CdC03. The evolution of C02 is probably catalyzed in the presence of water vapor and shifted to considerably... 

TOPICS RELATING TO THE STABILITY AND DECOMPOSITION OF TRANSITION METAL FORMYL COMPLEXES... 

The steric effects of the substituents, such as in 3,5-dialkylpyrazoles, may induce the coordination of small ligands or counterions that usually do not coordinate to transition metal ions. This behaviour is believed to be responsible for the unusual decomposition of transition metal tetra-fluoroborates in the presence of such ligands.43 Otherwise, the coordination number changes, resulting in, for example, square-planar Ni11 (low-spin) complexes, even with rather weak ligands such as 1,2-dimethylimidazole.44... 

Figure 13 Decomposition of transition metal carbene complexes through reductive elimination.

The thermal decomposition of transition metal complexes is often reported as a decomposition point in the form of m.p. n°C (decomp.) , e.g. ... 

Decompositions of transition-metal sulfides, notably those of Fe, Ni, Cu and Co, have been of technological importance in ore refining. Some of the published work is concerned with naturally-occurring minerals, while other studies used synthetic preparations. Reactions often proceed by a contracting interface mechanism and the rates are decreased when gaseous product is present, or its escape is opposed by an inert gas. On heating in air, several metal sulfides form sulfates or oxysulfates as intermediates in a sequence of reactions which finally yield metal oxides [43]. 

The initial or rate limiting step for anion breakdown in metal oxalate decompositions has been identified as either the rupture of the C - C bond [4], or electron transfer at a M - O bond [5], This may be an oversimplification, because different controls may operate for different constituent cations. The decomposition of nickel oxalate is probably promoted by the metallic product [68] (the activity of which may be decreased by deposited carbon, compare with nickel malonate mentioned above [65]). No catalytically-active metal product is formed on breakdown of oxalates of the more electropositive elements. Instead, they yield oxide or carbonate and reactions may include secondary processes [27]. There is, however, evidence that the decompositions of transition metal oxalates may be accompanied by electron transfers. The decomposition of copper(II) oxalate [69] (Cu - Cu - Cu°) was not catalytically promoted by the metal and the acceleratory behaviour was ascribed to progressive melting. Similarly, iron(III) oxalate decomposition [61,70] was accompanied by cation reduction (Fe " - Fe ). In contrast, evidence was obtained that the reaction of MnC204 was accompanied by the intervention of Mn believed to be active in anion breakdown [71]. These observations confirm the participation of electron transfer steps in breakdown of the oxalate ion, but other controls influence the overall behaviour. Dollimore has discussed [72] the literature concerned with oxalate pyrolyses, including possible bond rupture steps involved in the decomposition mechanisms... 

Alkali metal ions have never been found to promote hydride migration to form metal formyls in a manner analogous to cation-induced alkyl migration In fact small cations have been shown to enhance the rate of decomposition of transition metal formates (205) and to coordinate to and abstract hydride from transition metal hydrides (206). 

Table 6.1 Examples of metal NPs prepared in ILs by reduction or controlled decomposition of transition-metal compounds with hydrogen.

Two important modes of decomposition of transition-metal alkyls are a- and j5-elimination, while intramolecular reductive elimination, oxidative addition (e.g. y-elimination), and homolytic M—C bond fission are other pathways available. The formation of alkylidene complexes by a-elimination has been reviewed. The mechanism of a-elimination has received some attention recently but is not well worked out. The thermal decomposition of pentabenzyltantalum has the following stoicheiometry, although the nature of the Ta product is obscure ... 

Kurokawa H., Ishizaki T, Suzuki M. Preparation of refractory nitride fibers by thermal decomposition of transitional metal (Ti, Nb) alkoxide-cellulose precursor gel fibers in NH3 atmosphere. J.Mater. Sci. 2001 36 301-306... 

Kitaoka K., Koznka H., Yoke T. Preparation of lead lanthannm zirconate titanate (PLZT, (Pb,La)(Zr,Ti)03) fibers by sol-gel method. J. Am. Ceram. Soc. 1998 81 1189-1196 Koznka H., Knroki H., Sakka S. Flow characteristics and spinnability of sols prepared from silicon alkoxide solntion. J. Non-Cryst. Solids 1988 100 226-230 Kmger R., Glanbitt W., Lobmann P. Strnctnre evolntion in sol-gel-derived yttrium aluminum garnet-alumina precursor fibers. J. Am. Ceram. Soc. 2002 85 2827-2833 Kurokawa H., Ohta H., Sato T. Preparation of carbide fibres by thermal decomposition ofceUulose-metal (Ti, Zr) alkoxide gel fibres. J. Mater. Sci. Lett. 1994 13 516-518 Knrokawa Y., Ishizaki T., Suzuki M. Preparation of refractory nitride fibers by thermal decomposition of transition metal (Ti, Nb) alkoxide-cellnlose preenrsor gel fibres in NH3 atmosphere. J. Mater. Sci. 2001 36 301-306... 

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