Organometallic compound dispersion

The activity of chemically active AF paints usually relies on the reactivity of organometallic compounds (e.g. TBT-, Zn-, Si, Cu- acrylates and Zn-resinates) and inorganic pigments (i.e. CU2O). In spite of this, scanning electron microscopy coupled with energy dispersive X-ray detectors (SEM-EDX) has not been used extensively to characterise such reactions. Bishop and Silva... 

Homogeneous Catalysts The first of the aforementioned species may be considered examples of homogeneous catalysts. In addition, metal complexes and organometallic compounds arc important members of this class of catalysts. As the name implies, these catalysts arc uniformly dispersed or dissolved in a gas or liquid phase together with the reactant of the reaction. 

One major reason for the great interest in the processes of thin metal-containing films is that reactions on the surface of small metal clusters can be studied. Indeed, prior to the development of thin-film chemistry, reactions of similar particles were studied only in the gas phase at rather high temperatures. Under these conditions, most of the primary products are unstable and decompose in the course of further reaction, which is non-selective. As a result, the information obtained on the routes and mechanisms of reactions of disperse metals appears to be scarce, while the use of such reactions in synthesis is inexpedient. Conversely, low-temperature reactions in the films of co-condensates are very promising from the standpoint of determining the detailed reaction mechanism, as well as for synthesis of previously unknown complexes and organometallic compounds. It is important that atoms of only a few metals react with organic compounds immediately at the instant of their contact on the cooled substrate. Rather often, atoms and/or small (molecular) clusters are first stabilized in the film, and then their transformations are observed. 

Serp et al. [39] prepared activated carbon-supported platinum catalysts by chemical vapor deposition of organometallic compounds. They contacted carbon rods with a gas mixture containing He, 3% H2, and a 10 molar ratio of [Pt(CH3)2(COD)] (COD ri" -l,5-cyclooctadiene) for 12 minutes at 383 K and 50 torr. They concluded that preoxidation of the carbon support with HNO3 was a very important factor in obtaining well-dispersed platinum particles, as the oxygen surface complexes acted as anchoring centers for the platinum precursor. 

In solvated metal atom dispersion (SMAD) method solvated atoms prepared at very low-temperature are used as transient, highly reactive organometallic reagent for the deposition of Sn-Pt bimetallic particles onto different supports. In another approach chemical vapor deposition (CVD) using tin organometallic compounds was applied. For example, the selective reaction of Sn(CH3)4 vapour with Pt nanoparticles supported on Si02 appears to be very promising preparation method. 

Triple resonance 3D-NMR experiments can be useful for studying polymeric structures without resorting to isotopic labeling, even when the nuclei involved are present in low natural abundance. This study of MD3M shows that the considerable spectral dispersion obtained in the Si NMR spectra of siloxanes, compared with the narrow H and C chemical shift ranges, permits detailed examination of the structure of PDMS by the 3D H/ C/ Si NMR correlation experiment. These techniques can also be usefiil for characterizing star-branched polymers which contain NMR active nuclei, polymers with low concentrations of heteroatoms (e.g. at the chain end or at low occurrence branch points) and many organometallic compounds. 

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