Osmium occurrence

Using as catalyst precursors the clusters Os3H2(CO)i0 and Os3(CO)12 [71, 72], Laine and coworkers found a deuteration pattern of quinoline hydrogenation similar to that shown in Scheme 16.16, except for the presence of more deuterium in the 4-position and less in the 2-position, which has been interpreted in terms of the occurrence of oxidative addition of the osmium cluster to C-H bonds in quinoline, and also 1,4-hydrogenation (Scheme 16.17). 

In 1866 Friedrich Wohler discovered a ruthenium mineral. When he analyzed the shining black grains of what seemed to be an unusual platinum mineral which Herr Waitz of Cassel had brought back from Borneo, he found it to be a sulfide of ruthenium and osmium. Wohler stated that this mineral, which he named laurite, presented the first example of the natural occurrence of sulfur compounds of the platinum metals (129). 

The lower part of Figure 14.16 shows that the osmium(VI) derivatives C and E are formed when 0s04 reacts with alkenes in the absence both of a co-oxidant and water. The occurrence of C and E allowed to deduce that the osmium(VI) acid ester B (also) is an intermediate in the cis-vic dihydroxylation of alkenes when water is present. In the... 

Occurrence and History.—Osmium occurs in nature alloyed with iridium as iridosmine or osmiridium, which is found as irregular flattened grains and, more rarely, as hexagonal prisms. It has a metallic lustre, tin-white to light steel-grey in appearance hardness 6-7 density 19-3 to 21-12.1 It occurs in Choco, South America in the Urals in auriferous and other drifts in New South Wales in auriferous beach-sands of North California and also in gold washings of certain Canadian rivers.1... 

Occurrence in earth s crust about 0.001 ppm. Discovered in 1804 by Tennant. Occurs in nature in the metallic state, usually as a natural alloy with osmium (osmiridium) found in small quantities alloyed with native platinum (platinum mineral) or with native gold. Recovery and purification from osmiridium Deville, De-bray, Ann, Chim. phys. 61, 84 (1861) from the platinum mineral Wichers, J. Res. Nat. Bur. Stand. 10, 819 (1933). Reviews of prepn, properties and chemistry of iridium and other platinum metals Gilchrist, Chem. Rev. 32, 277-372 (1943) W p. Griffith, The Chemistry of the Rare Platinum Metals (John Wiley, New York, 1967) pp 1-41, 227-312 Livingstone in Comprehensive Inorganic Chemistry vol. 3, J. C. Bailar Jr. et at, Eds. (Pergamoti Press, Oxford, 1973) pp 1163-1189, 1254-1274. 

Natural occurrence. Osmium is an extremely rare element in the Earth s crust with an average abundance of 1 pg/kg (i.e., 1 ppb wt.). It naturally occurs as a native element alloyed with iridium and other PGMs in minerals such as osmiridium and in all platinum ores. 

Natural occurrence. Platinum metal occurs free in nature as a native metal contaminated with small amounts of all the PGMs such as iridium, osmium, palladium, ruthenium, and rhodium. These native minerals are found in placer ore deposits. 

The promoting role of halides in the isocyanate-producing reaction was ascribed to their ability to assume a bridging position in the cluster, likely weakening at the same time one of the N-Ru bonds and rendering the imido fragment more prone to attack a coordinated CO. The occurrence of such reactions was indeed confirmed by later studies on related osmium cluster [165], for which several intermediates could be isolated. 

In summary, there was no evidence beyond a doubt for superheavy elements in Nature. Since improved theoretical calculations of half-lives tended with time to reach much shorter values than those required for occurrence in Nature, the enthusiasm for further searches ceased in the early 1980s. This colorful intermezzo in superheavy element research appeared to be finished, but remarkably, a search for primordial element 108 (hassium) in its homolog osmium was recently undertaken [84]. 

Studies by Lenard and Singer (1968) on erythrocyte membranes treated with glutaraldehyde, osmium tetroxide, and potassium permanganate have shown a considerable decrease in a-helix content of the membrane protein which implies the occurrence of other structural changes as a result of these treatments. 

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