Platinum atom

Compound [PtCl( Bu2PCMe2CH2)2l reacts with pyrazole or 3,5-dimethyl-pyrazole in the presence of sodium hydroxide to form 242 (R = H, Me) [84ICA (82)L9]. The chelate ring is not planar in this case, and the trans strucmre of the pyrazolate derivative was demonstrated. Tlie four-coordinated platinum atoms are characterized by a distorted square-planar coordination. 

LEED, namely one with a, c(2x2) and one with a, p(2x2) superstructure. They are compatible with CusPt and CusPta layers. The first atomic layer was in both cases found by means of photoemission of adsorbed xenon to be pure copper. Details of the experimental work can be found in ref. 9 and 10. A schematic view of both structures can be seen in figure 1. Both consist of alternating layers of pure copper and of mixed composition. In the CuaPt case, the second and all other evenly numbered layers have equal numbers of copper and platinum atoms, whereas in the CusPta case the evenly numbered layers consist of thrice as many platinum as copper atoms. 

There is significant metal-metal bonding in the platinum compound, whose geometry involves a square of platinum atoms another important difference is that the coordination geometry is square planar in palladium acetate but octahedral in the platinum analogue. Different oligomers exist in solution, broken down by adduct formation. Palladium(II) acetate may be obtained as brown crystals from the following reaction [65] ... 

X 16.101 cis-Platin is an anticancer drug with a structure jQ that can be viewed on the Web site, (a) What is the formula and systematic name for the compound cis-jf Platin (b) Draw any isomers that are possible for this compound. Label any isomers that are optically active, (c) What is the coordination geometry of the platinum atom ... 

X-Ray structural analysis of [Pt(dithiocumato)2] revealed a dimeric structure containing two bridging and two terminal dithiocarboxylate ligands (XXXII). The proximity of the two platinum atoms (278 pm) suggested that a Pt-Pt bond may be present (415). 

Short nonbonded Si—Si distances have been observed in four membered metallacycles (Scheme 12b) with a Pt, Ir, W, or Nb atom [138-142] in place of one of the oxygen (nitrogen) atoms of 1,3-cyclodisilazanes (1,3-cyclodisilazanes) and in U-silylene-bridged dinuclear platinum complexes (Scheme 12c) [143, 144]. Electron donating occupied orbitals are expected to be on the platinum atoms like lone pair orbitals on the oxygen atoms in cyclodisiloxanes. 

Supported bimetallic Re—Pt catalysts are important in selective reforming of petroleum. It is believed that sulhding the catalyst before use gives ReS units which act as inert diluents to reduce the size of a local ensemble of platinum atoms. Selectivity for desirable dehydrocyclization and isomerization reactions... 

When tetranuclear platinum complex (35) bridged by tetra(4-ethynylphenyl)-methane was used as the core (Fig. 6), dendrimers having more platinum atoms than those prepared from trinuclear platinum core 30 in the molecule were obtained up to the third generation. GPC analysis of these dendrimers revealed that the dendrimers with a tetraplatinum core have a similar molecular size to those with the triplatinum core 30. 

The majority of crystallites observed were 3 or 4 nm In size. In Figure 3, a bar graph Illustrates the size range distribution and a comparison of mass variation for the 3 and 4 nm crystallite sizes. Although only thirty analyses were oiade, overall visual analysis confirmed the presence of hundreds of 3 to 4 nm platinum crystals with negligible numbers less or greater than these dimensions. It appears that slight variations In crystallite diameter and thickness have resulted In a fairly uniform number of platinum atoms per crystallite for the majority of the crystallites analyzed. In order to normalize count rates, the decrease In the field emission Intensity was taken Into account. 

In conclusion, hydrogenolysis processes and coke formation occur on large ensembles of surface platinum atoms [160], while dehydrogenation reactions would proceed on single (isolated) Pt atoms [169]. The presence of tin atoms regularly distributed on the metal surface diminishes the size of the ensemble [130,170-173], the same is observed for copper atoms on nickel surfaces [174] or tin atoms on rhodium and nickel surfaces [137,175-177], leading to site isolation and therefore to selectivity. 

FIGURE 27.16 Cu full layer in sulfate solution (structural model used for FEFF6 calculations) (a) side view (b) top view. Thin solid line platinum atoms dashed hne copper atoms thick solid line oxygen atoms. (From Soldo et al., 2002, with permission from Elsevier.)... 

Arene and olefin compounds, pure or in admixture, are efficient ligands in promoting the aggregation of platinum atoms from mononuclear species to ligand-stabilized soluble clusters and solid-supported nanoparticles (Scheme 14). 

A series of mixed-ligand thiosalicylato complexes of the type PtL(PPh3)Y2] (Y2 = thiosalicylate L = pyridine, 4-methylpyridine, picolinic acid hydrazide, imidazole) have been prepared by the reaction of [PtCl2(COD)] with PPh3, thiosalicylic acid, and A-donor ligand in MeOH solution.375 The X-ray structure of the pyridine derivative (162) was determined, the first example of where a platinum atom is coordinated to a N, O, P, and S donor atom set. 

Alternatively, it is of course possible to formulate this using only a single platinum atom... 

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