Platinum band structure

The distances found between platinum centers in these molecules have been correlated with the resonating valence bond theory of metals introduced by Pauling. The experimentally characterized partially oxidized one-dimensional platinum complexes fit a correlation of bond number vs. metal-metal distances, and evidence is presented that Pt—Pt bond formation in the one-dimensional chains is resonance stabilized to produce equivalent Pt—Pt distances.297 The band structure of the Pt(CN)2- chain has also been studied by the extended Huckel method. From the band structure and the density of states it is possible to derive an expression for the total energy per unit cell as a function of partial oxidation of the polymer. The equilibrium Pt-Pt separation estimated from this calculation decreases to less than 3 A for a loss of 0.3 electrons per platinum.298... 

The platinum structure is FCC (see Figure 2.4) and the electronic arrangement of Pt is [Xe]5d96s1]. The band structure of platinum is also the cause of its catalytic properties. Platinum does not form very strong, nor weak bonds, and is, consequently, one of the most active among the transition metals in several reactions. In fact, platinum is a multipurpose, heterogeneous metallic catalyst,... 

Fig.1.5. Self-consistent energy-band structure for fee platinum obtained similarly to that of tungsten on the previous figure...

Fig.2.10. Self-consistent, fully hybridised energy-band structure for nonmagnetic chromium obtained as for tungsten and platinum, Figs.1.4,5. Comparison with the unhybridised bands in the previous figure gives a feeling for the accuracy one may obtain within the very simple unhybridised canonical band theory. It also gives an idea of the effect and importance of hybridisation, defined essentially as the difference between the two figures...

Compounds of a large number of catalytically toxic metals, including toxic metallic ions. This subject will also be developed in greater detail below and it will be shown that the possession of a toxic character towards, for instance, a platinum catalyst seems to be determined by the d-band structure of the adsorbed metal. This type of poison does not usually lend itself to detoxication. 

Recently Whitmore (572) has performed an electron energy band structure calculation for linear square planar platinum complexes using a multiple scattering technique and a potential determined from a self-consistent calculation of the unit cell. The calculation was evaluated for uniform Pt-Pt spacings of 2.8 and 2.9 A. For Pt-Pt spacing of 2.9 A, the electron energy band derived... 

The metallic, strong bonds are shown in Fig. 1.5 for the example of lithium, Li. In this case the electrons are not concentrating in an identifiable bond, but are shared in a band structure. Such arrangement makes the bonds, as in the LiF non-directive, but it also removes all packing restrictions. Metals can thus pack most closely, often with a CN of 12. The most dense materials are found among the heavy metals (osmium, iridium, platinum, and gold have densities of 19-22 g cm compared to water with the density of 1.0 g cm" ). 

Let us try to predicf qualitatively (without making calculations) the band structure of a stack of platinum square planar complexes, typically [Pt(CN )4 ]co- Con-... 

Let us try to predict" qualitatively (without making calculations) the band structure of a stack of platinum square planar complexes - typically [Pt(CN )4 ]oo. Consider the eclipsed configuration of all the monomeric units. Let us first simplify our task. Who likes cyanides Let us throw them away and take something theoreticians really love H . This isn t just laziness. If needed, we are able to make calculations for cyanides too, but to demonstrate that we really understand the machinery, we are always recommended to make the system as simple as possible (but not simpler). We suspect that the main role of CN is just to interact electrostatically, and H does this too (being much smaller). In reality, it turns out that what decides is the Pauli exclusion principle, rather than the ligand charge." " ... 

FIGURE 8.2 Calculated -projected density of states (DOS) for a number of platinum clusters in the cuboctahedron structure. The figure clearly shows the transition between a continuous band structure of highly delocalized electrons for large clusters (>2nm) and the more discrete energy levels for smaller clusters. For comparison, the ealculated s-projeeted DOS for Pt( 111) is shown as well. We note the resemblance between the DOS for the Pt and the Pt(lll) slab, suggesting that already at sizes above 2nm, the band structure is close to converge to the metallic state. 

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