Degree of metallization

Solution processes of complexes of Mo(VI), W(VI) and V(V) with BPR as well as these complexes in the presence of dodecylpyridiniy chloride from aqueous solutions on aminosilica gels surfaces have been considered. The presence of dodecylpyridiniy chloride increases significantly the sorption degree of metals and broadens pH range of their quantitative extraction. 

Galvanic corrosion typically involves two or more dissimilar metals. It should be recognized, however, that sufficient variation in environmental and physical parameters such as fluid chemistry, temperature (see Case History 16.3), flow velocity, and even variations in degrees of metal cold work can induce a flow of corrosion current even within the same metal. 

The short Au Ag contacts may be due to some degree of metal-metal bonding which means that these were the first reported Au—Ag bonds. The complexes with acetone and acetonitrile shown are also the first reported examples in gold chemistry in which the pentafiuorophenyl ligands act as a bridge between Au and Ag centers. This type of behavior is generally more common in Pt chemistry. 

Hardiman R.T., Banin A., Jacoby B. The effect of soil type and degree of metal contamination upon uptake of Cd, Pb and Cu in bush beans. Plant Soil 1984b 81 3-15. 

For catalysts reduced at 400°-500°C, average nickel particle diameters in the range 30-45 A (40,43), and 30-200 A (41) have been quoted. Coenen and Linsen (41) have assumed a roughly hemispherical shape for the nickel particles which expose (111), (100), and (110) planes, and this is at least consistent with the very limited electron microscopic evidence. On the whole, it appears to be more difficult to produce a very high degree of metal dispersion with nickel than with platinum, and it is very difficult to obtain an average nickel particle diameter <30 A, although not impossible. 

P 162 x 1CT4 cm-1, k0 0.5, c2 0.9, and fry 0.9 (= V23 0.5), indicating only a small degree of metal-ligand interaction for the level. It was suggested by Rettig etal. (65) that the metal orbitals (5 ) of Mn(Cp)2 were more involved in back donation to the ring than in Fe(Cp)2+ (q.v.) by virtue of the smaller apparent k values found for the former (ca. 0.5 vs. ca. 0.8). However, since the calculated parameter is actually fcy 23 this conclusion cannot be substantiated since only the product of k and V23 is currently known for Fe(Cp)2+. 

It is generally assumed that force constant is a measure of valence bond order. If so, this would imply that the force constant of a coordinated CO group would be a direct measure of the degree of metal-ligand back-donation. 

Tetrametallic cubane clusters are the ones most frequently dealt with in MO treatments with respect to the degree of metal-metal bonding. Qualitative MO arguments have rationalized the geometries adopted by [CpFe(C0)]4 (- 75),... 

The performance of a catalyst is well known to be sensitive to its preparation procedure. For this reason, ideally an oxide-supported metal catalyst should be subjected to a number of characterization procedures. These may include measurements of the metal loading within the overall catalyst (usually expressed in wt%), the degree of metal dispersion (the proportion of metal atoms in the particle surfaces), the mean value and the distribution of metal particle diameters, and qualitative assessments of morphology including the particle shapes and evidence for crystallinity. These properties in turn can depend on experimental variables used in the preparation, such as the choice and amounts of originating metal salts, prereduction, calcination or oxygen treatments, and the temperature and duration of hydrogen reduction procedures. 

M4E4 (38-41) compounds where the total number of valence electrons, Z, is directly related to the degree of metal-metal bonding in the M3 resp. M4 frameworks. Table I summarizes their results. 

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