Palladium Pd

The most sensitive analytical lines for palladium are at 244.791 nm and 247.642 nm with characteristic concentrations of cq = 0.064 mg/L and cq = 0.10 mg/L, respectively, in a very fuel-lean air / acetylene flame, whereby the former exhibits a highly non-linear calibration curve. The characteristic mass at the second line, using a transversely heated graphite tube atomizer, is about mo = 22 pg. 

Palladium has about 50 absorption lines of significantly different sensitivity. However, as there is only very rarely any need to determine high concentrations of palladium, only a few selected lines are shown in Table 6.19, together with information about then-spectral environment. 

Name Formula State Color Solubility AG° (kJ/mole) 

Some log Pn values for Pd+ are NH3 (9.6, 18.5, 26.0, 36.3), OH (13.0, 25.8, 29.4, 42.2). By oxidation PdXg complexes (X = Cl, Br, 1) can be formed from the PdX4 complexes, but they are thermodynamically unstable. However, they have a tendency to be inert, which means their decompositions occur slowly. 

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The platinum-group metals (PGMs), which consist of six elements in Groups 8— 10 (VIII) of the Periodic Table, are often found collectively in nature. They are mthenium, Ru rhodium, Rh and palladium, Pd, atomic numbers 44 to 46, and osmium. Os indium, Ir and platinum, Pt, atomic numbers 76 to 78. Corresponding members of each triad have similar properties, eg, palladium and platinum are both ductile metals and form active catalysts. Rhodium and iridium are both characterized by resistance to oxidation and chemical attack (see Platinum-GROUP metals, compounds). 

It was found that sorbed palladium might catalyse reaction of Mn(III) reduction by Cf not only after it s removing from coal, but AC with palladium, Pd/AC, has also his own catalytic effect. On the base of dependence between characteristics of AC, chemical state of palladium on AC surface and catalytic action of Pd/AC in indicator reaction it might establish, that catalytic action concerns only to non-reduced or partly reduced palladium ions connected with chloride ions on coal surface. The presence or absence of catalytic action of Pd/AC in above-mentioned reaction may be proposed for determination of chemical state of palladium on AC surface. Catalytic effect was also used for palladium micro-amounts determination by soi ption-catalytic method. 

Palladium (Pd) is an element with properties similar to those of platinum. It is useful in eliminating harmful emissions produced by internal combustion engines. Two students were given identical cylindrical palladium bars with die following data ... 

B. (E)-4-(2-Phenylethenyl)benzonitrile (2). An oven-dried, 250-mL, three-necked, round-bottomed flask equipped with an argon inlet adapter, rubber septum, glass stopper, and a teflon-coated magnetic stir bar is cooled to room temperature under a flow of argon. The flask is charged successively with bis (tri-tert-butylphosphinc)palladium [(Pd(P(t-Bu)3)2] (0.238 g, 0.466 mmol, 1.5 mol% Pd) (Notes 1, 2), tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3) (0.213 g, 0.233 mmol, 1.5 mol% Pd) (Note 3), and... 

A particularly interesting case is that of the platinum metal group which, in addition to platinum (Pt), comprises ruthenium (Ru), osmium (Os), rhodium (Rh), iridium (Ir), and palladium (Pd). These carbonyl halides are usually the most practical precursors for metal deposition because of their high volatility at low temperature. Indeed two of them, palladium and platinum, do not form carbonyls but only carbonyl halides. So does gold. 

The platinum-group metals comprise ruthenium (Ru), rhodium (Rh) and palladium (Pd) from the second transition series and osmium (Os), iridium(Ir), and platinum (Pt) from thethird transition series. Little or no C VD investigation of palladium and osmium have been reported and these metalsarenotincludedhere. The properties of the other platinum-group metals are summarized in Table 6.9. 

Alkenylboranes (R2C=CHBZ2 Z — various groups) couple in high yields with vinylic, alkynyl, aryl, benzylic, and allylic halides in the presence of tetra-kis(triphenylphosphine)palladium, Pd(PPh3)4, and a base to give R C CHR. 9-Alkyl-9-BBN compounds (p. 1013) also couple with vinylic and aryl halides " as well as with a-halo ketones, nitriles, and esters.Aryl halides couple with ArB(IR2 ) species with a palladium catalyst. ... 

These results show that important performance benefits are obtained by the addition of Au and KOAc to a palladium catalyst. Gold (Au), when added to palladium (Pd), enhanced the VAM production rate of the catalyst (VAM STY) substantially while it decreased the overall selectivity of the catalyst. This is true in both cases Pd-Au w/KOAc vs. Pd w/KOAc (764 vs. 100 93.6% vs. 95.4%) and Pd-Au vs. Pd (594 vs. 124 91.6% vs. 94.7%). Conversely, KOAc increased the selectivity of the catalyst whether or not Au is used. In the most appetizing example (Pd-Au w/KOAc vs. Pd-Au), KOAc improved the selectivity of the catalyst by 2.0% while it additionally improved the production rate of die ca yst 30%. KOAc only increased the production rate of the catalyst in the presence of Au. KOAc decreased the VAM production rate of the catalyst on its addition to the Pd catalyst where Au was absent. 

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