Group VIII Iron, Ruthenium, and Osmium

Group VIII Iron, Ruthenium, and Osmium 6.1 Iron Carbonyl Complexes.- Stepwise degradation of S(NSiMe2)2 occurs on reaction with Fe (CO) 2 giving [Fe2(CO)g(Me SiNS)]... 

Group VIII Metals Iron, Palladium, Rhodium, Ruthenium, and Osmium... 

Catalysts. The methanation of CO and C02 is catalyzed by metals of Group VIII, by molybdenum (Group VI), and by silver (Group I). These catalysts were identified by Fischer, Tropsch, and Dilthey (18) who studied the methanation properties of various metals at temperatures up to 800°C. They found that methanation activity varied with the metal as follows ruthenium > iridium > rhodium > nickel > cobalt > osmium > platinum > iron > molybdenum > palladium > silver. 

We place hydrogen as the first element in the first period, along with helium. When helium was discovered, Mendeleev put it in the second period. We put the triads of iron, cobalt, and nickel ruthenium, rhodium and palladium and osmium, iridium, and platinum in group VIIIB, in the middle of the table. Mendeleev put them in group VIII. We also have two long groups, the lanthanides and actinides, that were a headache for Mendeleev. 

In Group VIII, each position instead of being filled by a single element is occupied by a group of three elements. Thus there appear in triads iron, cobalt, and nickel ruthenium, rhodium, and palladium and osmium, iridium, and platinum. In this group there is no subdivision into families, but all the members are heavy metals. 

Titanium is the only member of its family forming +3 compounds of appreciable stability (Zr, Hf, and Th are almost exclusively tetravalent). In group Va, only vanadium assumes a +4 oxidation state (its congeners almost invariably are pentavalent). In Group VIII, osmium and ruthenium can assume a valence of + 8, but their lighter congener, iron, apparently does not. 

Iron (Fe), cobalt (Co) and nickel (Ni) are sometimes called iron group metals while ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt) are known as platinum group metals. Metals of each group have similar physical and chemical properties. Table 2.73 sununarizes some physical properties of group-VIII metals. 

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