Osmium atomic properties

The results of the EXAFS studies on osmium-copper clusters lead to conclusions similar to those derived for ruthenium-copper clusters. That is, an osmium-copper cluster Is viewed as a central core of osmium atoms with the copper present at the surface. The results of the EXAFS investigations have provided excellent support for the conclusions deduced earlier (21,23,24) from studies of the chemisorption and catalytic properties of the clusters. Although copper is immiscible with both ruthenium and osmium in the bulk, it exhibits significant interaction with either metal at an interface. 

Occurronco and History of Osmium -Preparation -Properties Colloidal Osmium—Catalytic Activity—Atomic Weight—Uses Alloys. 

The stmcture, the properties in solution and the coordination chemistry of 1 and 20 are similar. However, the intrinsically higher basicity of the osmium atom... 

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). 

Because of- the similarity in the backscattering properties of platinum and iridium, we were not able to distinguish between neighboring platinum and iridium atoms in the analysis of the EXAFS associated with either component of platinum-iridium alloys or clusters. In this respect, the situation is very different from that for systems like ruthenium-copper, osmium-copper, or rhodium-copper. Therefore, we concentrated on the determination of interatomic distances. To obtain accurate values of interatomic distances, it is necessary to have precise information on phase shifts. For the platinum-iridium system, there is no problem in this regard, since the phase shifts of platinum and iridium are not very different. Hence the uncertainty in the phase shift of a platinum-iridium atom pair is very small. 

Hirschmann M. (1991). Thermodynamics of multicomponent olivines and the solution properties of (Ni,Mg,Ee)2Si04 and (Ca,Mg,Fe)2Si04 olivines. Amer. Mineral, 76 1232-1248 Hirt B., Herr W, and Hoffmeister W. (1963). Age determinations by the rhenium-osmium method. In Radioactive Dating, International Atomic Energy Agency, Vienna. 

A study of the chemical properties of iridium and its compounds shows that, whilst closely resembling platinum in many respects, it forms a fitting link between that element and osmium. With an atomic weight intermediate in value between 190-9 (at. wt. of osmium) and 195-2 (at. wt. of platinum), iridium falls into a suitable position in the Periodic Table where these analogies are recognised. 

The Grouping of Elements into Triads—Atomic Weights of the Elements— General Properties of tho Elements—Comparative Study of Iron, Cobalt, and Nickel—Their Position in tho Periodic Table—Comparative Study of Iron, Ruthenium, and Osmium—Comparative Study of Cobalt, Rhodium, and Iridium—Comparative Study of Nickel, Palladium, and Platinum. 

The change in the chemical properties of ammonia which results from coordination is due to the drawing of electronic density from the molecule toward the acceptor center. The most immediate consequence of this is an increase in the acid strength of the hydrogen atoms of the ammonia (5). This is most pronounced for complexes with platinum(IV), osmium(IV), gold(III), and other ions of heavy platinum metals. 

Osmocene, Os( sHo)2, has recently been made, in 20% yield, by the interaction of cyclopentadienyl sodium and osmium tetrachloride (47). It forms colorless crystals which melt at 230° again, it dissolves in organic solvents water, however, has no action on it, nor does it dissolve. The hydrogen atoms in the cyclopentadienyl rings, like those in ferrocene and ruthenocene, can undergo substitution this property has not been described for other metal cyclopentadienyl compounds, except in one... 

From Figure 4.12 it can be seen that the modified amplitude function is very different for osmium and copper, reflecting differences in their electron scattering properties and in the parameter o-,. As a result, osmium and copper atoms can be distinguished from each other without too much difficulty when one attempts to obtain information on the number of neighbor atoms of a given type that surround osmium or copper atoms in bimetallic clusters of these two elements. 

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