Group VIII/18 elements

Furan derivatives of group VIII elements 97KGS154. 

Neutral Binary Carbonyls of Group VIII Elements... 

The reactions of the Group VIII elements with 1,5-COD have been examined in detail and in each case a similar product is obtained ... 

Formation of Two Bonds Four-Atom Fragment and a Nitrogen, Phosphorus, or Group VIII Element... 

In the last few years, numerous stable, diamagnetic oxygen complexes of other Group VIII elements (Ir, Rh, Ru, Os, Ni, Pd, Pt) have been prepared.147-151... 

The aerobic oxidation of alcohols catalysed by low-valent late-transition-metal ions, particularly those of group VIII elements, involves an oxidative dehydrogenation mechanism. In the catalytic cycle (Fig. 5) ruthenium can form a hydridometal species by /1-hydride elimination from an alkoxymetal intermediate, which is reoxidized by dioxygen, presumably via insertion of 02 into the M-H bond with formation of H202. Alternatively, an alkoxymetal species can decompose to a proton and the reduced form of the catalyst (Fig. 5), either directly or via the intermediacy of a hydridometal intermediate. These reactions are promoted by bases as cocatalysts, which presumably facilitate the formation of an alkoxymetal intermediate and/or /1-hydride elimination. 

These attempts to synthesize five-membered ring system failed due to the low reactivity of the CH2C1 group or the formation of unsuitable isomeric trans compounds. The addition of the SiH group to a C=CH group occurs as a cis addition when catalysts of group-VIII elements are present37) a trans olefine subsequently formed ... 

In what ways are group IB elements and group VIII elements exceptions to the rule that the maximum oxidation number is usually equal to the group number ... 

Copper and gold have oxidation numbers that exceed the group number. Most group VIII elements have maximum oxidation numbers that are not as large as the group number. 

Catalytic Properties of Group VIII Elements and Their Compounds... 

Linear or cyclic oligomers containing some conjugated double bonds can be obtained from allene or its superior homologs, eventually in the presence of 1,3-butadiene or acetylene (in the latter case co-oligomers result)5. Transition metal complexes, in particular low-valence complexes of Group VIII elements, were found to be the best catalysts. Dehydrogenation reactions, carried out on cis-1,4- or tram-1,4-polybutadiene and in the presence of chloranil, quantitatively yielded polyacetylene within 8—15 hours at 130 °C6. ... 

Adsorption studies which have been conducted on the group VIII elements using other techniques will then be reviewed in a systematic sequence. This will be followed by the CO adsorption properties of the remainder of the transition metals. In all these sections, a comparison between the results being described and those previously discussed for the tungsten system will be made wherever possible. Finally, any overall conclusions that emerge for CO adsorption will be indicated. 

Although infrared studies of adsorbed species have in no way been limited to the group VIII elements, there is a preponderance of literature devoted to this group of metals—notably nickel—and it will, therefore, be useful to discuss the technique as directed towards an understanding of CO adsorption on these metals. 

It can be seen (Fig. 20) from the results of Brennan and Hayes 80) on evaporated iron films that the initial CO calorimetric heat of adsorption is low (about 40 kcal/mole) in comparison with the 100 kcal/mole measured on tungsten and its nearest neighbors. This value obtained for the initial heat of adsorption of CO on iron films is very close to the values measured by these authors on all the other group VIII elements studied (Ni, Co, Rh, Pd, and Pt). 

In the table, group VIII elements (Helium, Neon, Argon, etc.) are all non-reactive gases, and group I elements (beginning with Lithium) are aii highiy reactive, are ductile metals, and react 1 1 with group VII elements. 

Other Group VIII elements can also be used as catalysts for oxygenates. Ichikawa and Shikakura reported interesting results on Pt catalysts, prepared from either [Pt3(CO)e] 2NEt4 n = 3-5) or from H2PtCl6, impregnated on to an oxide, as indicated in Figure 4. 

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