Group 10 Palladium Platinum

Hydrogenation Catalysts. The key to catalytic hydrogenation is the catalyst, which promotes a reaction which otherwise would occur too slowly to be useful. Catalysts for the hydrogenation of nitro compounds and nitriles are generally based on one or more of the group VIII metals. The metals most commonly used are cobalt, nickel, palladium, platinum, rhodium, and mthenium, but others, including copper (16), iron (17), and tellurium... 

Palladium, platinum, or nickel, supported or unsupported, are the metals usually used in nitro-group reductions. The choice of catalyst often depends on what other functions are present and on the products desired,... 

The most widely used methods for the application of coatings of gold, silver and the platinum group metals (platinum, palladium, rhodium, iridium, ruthenium, osmium) to base metals are mechanical cladding and electroplating. 

In their electrochemical surface properties, a number of metals (lead, tin, cadmium, and others) resemble mercury, whereas other metals of the platinum group resemble platinum itself. Within each of these groups, trends in the behavior observed coincide qualitatively, sometimes even semiquantitatively. Some of the differences between mercury and other. y- or p-metals are due to their solid state. Among the platinum group metals, palladium is exceptional, since strong bulk absorption of hydrogen is observed here in addition to surface adsorption, an effect that makes it difficult to study the surface itself. 

This volume is concerned with fundamental developments in the coordination chemistry of the elements of Groups 9-12 since 1982. The individual chapters cover the coordination chemistry of cobalt, iridium, nickel, palladium, platinum, copper, silver and gold, zinc and cadmium, and mercury. Unfortunately, because of factors beyond the Editors control, the manuscript for the proposed chapter on rhodium was not available in time for publication. 

Rare, shiny, and lightest metal of the platinum group. Hardens platinum and palladium. The presence of 0.1 % of ruthenium in titanium improves its resistance to corrosion 100-fold. The spectacular catalytic properties of ruthenium are used on industrial scales (hydrogenations, sometimes enan-tioselective, and metathesis). Titanium electrodes coated with ruthenium oxide are applied in chlorine-alkaline electrolysis. Suitable for corrosion-resistant contacts and surgical instruments. 

Nitro Compounds. Under mild conditions, aromatic nitro compounds are hydrogenated easily to amines.518 The reaction may give partially reduced products, according to the circumstances. Palladium, platinum, and nickel are used frequently for this reaction. For example, nitro and benzyl ester functions are reduced on Pd(OH)2/C on THF and on Pd/C in EtOH.519 Aliphatic nitro groups are reduced more slowly. 

Khulbe and Mann [155] have obtained infrared spectra of allene adsorbed on silica-supported cobalt, nickel, palladium, platinum and rhodium. The spectra were similar for all the metals, although variations in band intensity from metal to metal were observed. Addition of hydrogen to the allene-precovered surface resulted in similar spectra to those found for chemisorbed and hydrogenated propene in which the surface species was thought to be an adsorbed prop-1-yl group. The authors concluded that the initial allene spectrum was consistent with the adsorbed species being a 1 2-di-o-bonded allene (structure K)... 

Because of the creative minds contributing to the field, the tools of C-H bond transformation available to synthetic chemists are actively expanding [1], Among these, coordination-directed C-H bond-activation has long preserved its appeal, because it enables selective functionalization of a particular C-H bond in the presence of other functional groups. This can be achieved by using a heteroatom (FG = functional group shown in Scheme 1) in the substrate structure to direct the metal complex to the proximity of the specific C-H bond. Even unactivated sp3-centered C-H bonds tend to react in a cyclometalation step with palladium, platinum [2], and ruthenium catalysts [3]. 

Our laboratory first called attention to the bacterial effects of the simpler complexes in 1965. Over the next few years, in cooperative studies with microbiologists, a number of papers were published describing a multiplicity of effects on microorganisms caused by various complexes of platinum group metals platinum, palladium, ruthenium, rhodium, osmium, and iridium. 

The six platinum group metals, platinum, palladium, ruthenium, osmium, rhodium, and iridium, usually occur together in nature. These metals are not often found in artifacts. These metals are rare and have only been widely used in industry and for ornaments since the early twentieth century. Most platinum used today is as a catalyst in the systems used to control car exhaust emissions, in dentistry, and to make surgical tools, jewelry, and electrical equipment. 

Rylander and Rakoncza compared the rates of hydrogenation of pyridine V-oxide over 5% palladium-, platinum-, rhodium-, and ruthenium-on-carbon in methanol, water, and acetic acid.224 Rhodium was always the most active, although the pyridine ring was hydrogenated concomitantly with the reduction of the V-oxide group. 

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