Osmium and Iridium

Carbene and Carbyne Complexes of Ruthenium, Osmium, and Iridium... 

Examples of the osmium and iridium complexes are Os(PPh3)2Cl(NO) and Ir(PPh3)3(NO), respectively [216]. The osmium compound gave, on reaction with HC1, the first characterized complex with the feature of an N-coordinated HNO, Os(PPh3)2Cl2(HNO), which was confirmed by X-ray crystallography. On the other hand, the nitrosylated iridium compound gave the hydroxylamine complex [216]. 

Because of the importance of olefin metathesis in the industrial production of olefins and polymers, many different catalysts have been developed. Almost all of these are transition metal-derived, some rare exceptions being EtAlCl2 [758], Me4Sn/Al203 [759], and irradiated silica [760]. The majority of catalytic systems are based on tungsten, molybdenum, and rhenium, but titanium-, tantalum-, ruthenium-, osmium-, and iridium-based catalysts have also proven useful for many applications. 

Osmium - the atomic number is 76 and the chemical symbol is Os. The name derives from the Greek osme for smell because of the sharp odor of the volatile oxide. Both osmium and iridium were discovered simultaneously in a crude platinum ore by the English chemist Smithson Tennant in 1803. 

Sir Humphry Davy attempted to isolate this unidentified element through electrolysis—but failed. It was not until 1824 that Jons Jakob Berzehus (1779—1848), who had earlier discovered cerium, osmium, and iridium, became the first person to separate the element silicon from its compound molecule and then identify it as a new element. Berzehus did this by a two-step process that basically involved heating potassium metal chips with a form of silica (SiF = silicon tetrafluoride) and then separating the resulting mixture of potassium fluoride and silica (SiF + 4K —> 4KF + Si). Today, commercial production of sihcon features a chemical reaction (reduction) between sand (SiO ) and carbon at temperatures over 2,200°C (SiO + 2C + heat— 2CO + Si). 

Platinum is a relatively rare earth metal usually found with related metals osmium and iridium. While it has a number of industrial applications, its common consumer application is in catalytic converters. This application has actually increased platinum concentrations in roadside dust. The ability of platinum and its derivatives to kill cells or inhibit cell division was discovered in 1965. Platinum-based drugs, such as cisplatin, are used to treat ovarian and testicular cancer, and cancers of the head and neck, as well as others. Unfortunately, the toxic side effects of these agents often limit their usefulness. 

The earliest scientific descriptions of platinum, are those of Dr. Brownrigg and Don Antonio de UUoa in the middle of the eighteenth century. Rhodium, palladium, osmium, and iridium were discovered in 1803 and 1804, the first two by Dr. Wollaston and the others by his friend, Smithson Tennant. Thomsons History of Chemistry and Berzelius correspondence and diary present a pleasing picture of these two great English chemists. Ruthenium, the Russian member of the platinum family, was discovered much later by Karl Karlovich Klaus, whose life story was beautifully told by Professor B. N Menschutkin of the Polytechnic Institute of Leningrad. 

In 1828 Berzelius and G. W. Osann (25), professor of chemistiy at the University of Dorpat, examined the residues left after dissolving crude platinum from the Ural mountains in aqua regia. Berzelius did not find in them any unusual metals except palladium, rhodium, osmium, and iridium, which had already been found by Wollaston and Tennant in similar residues from American platinum. Professor Osann, on the other hand, thought that he had found three new metals, which he named pluranium, ruthenium, and polinium (25, 36). In 1844, however, Professor Klaus, another Russian chemist showed that Osann s ruthenium oxide was very impure, but that it did contain a small amount of a new metal (26,33). 

Birth of Smithson Tennant, the discoverer of osmium and iridium, at Wensleydale, Yorkshire. 

Feb. 6, 1804 1804 Oct. 6, 1807 Wollaston discovers palladium and rhodium. Death of Priestley at Northumberland, Pa. Smithson Tennant discovers osmium and iridium. Davy isolates potassium. A few days later he isolates sodium. 

In the course of investigating the production of platinum from its ores, Wollaston and Tennant found four new elements in 1803. Tennant isolated osmium and iridium Wollaston found rhodium and palladium. As was the contemporary habit, Wollaston named the latter after a newly discovered celestial body. Uranium gained its name this way after William Herschel s discovery of the planet Uranus, and palladium honoured the asteroid Pallas, found in 1802. 

This compound is the only one known for these elements in this oxidation state it is obtained as a highly-colored solid by the high-temperature reaction between fluorine and the metal. The solid is isostructural with the hexafluorides of osmium and iridium, and the Pt-F distance has been estimated at 1 83 A by extrapolation along the series W-Os-Ir 255). The infrared spectrum has been assigned in Oh symmetry 256) there are no signs of any distortion, as found for example in osmium hexafluoride. 

In addition to the encyclopedia of Gmelin and of Pascal, Griffith125 has written a comprehensive book about the chemistry of ruthenium, rhodium, osmium and iridium, and Hartley126 two volumes about palladium and platinum with emphasis on metallo-organic chemistry. 

Osmiridium is a native alloy of osmium and iridium it is extremely hard, and it is used for pointing gold pens and for the bearings of small wheels. An alloy of platinum with 10 per cent, of iridium is the metal employed for, crucibles. 

Copper is another transition metal that does not corrode easily, which makes it useful for water pipes. Copper is also an excellent conductor of heat, which explains why copper-bottomed cooking pans have been used for centuries. Today, most copper is used in electrical wiring, since it conducts electricity so well and can be stretched into thin shapes. Other transition metals that resist corrosion include platinum, osmium, and iridium. These last two elements are often used in metal pen nibs (the tip of a fountain ink pen) and the tip of spark plugs for cars. 

The four metals rhodium, palladium, osmium and iridium, share the same centennial and have been dealt with together.147-149 Wollaston separated palladium from platinum ore in 1803 but concealed the identity of the metal until 1804.150 Osmium was isolated from crude platinum by Smithson Tennant in 1804.151 There are accounts of the discoveries of niobium (by Hatchett)152 and ruthenium.153,154... 

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. 

A new class of binuclear nitrido complexes of tetravalent osmium and ruthenium is described in which the metal atoms are symmetrically bridged by a nitride ligand to give a linear M-N—M unit They have the stoichiometries M2NX8(H20)2]3 and [M2N(NH3)8Y2]3+ (M = Os, Ru X = Cl, Br Y = Cl, Br, etc.). Studies are reported on their vibrational spectra, structures, and bonding. Preliminary studies are reported also on trinuclear complexes of osmium and iridium. Finally, the use of vibrational spectroscopy in the study of metal-nitrido and metal-oxo complexes is discussed briefly. 

Osmium and iridium catalysts have been shown to be highly selective for the formation of unsaturated alcohols by hydrogenation of a,P-unsaturated aldehydes without any additive. Good yields of allyl alcohol (73%), crotyl alcohol (90%), and cinnamyl alcohol (95%) (eq. 5.26) were obtained by the hydrogenation of acrolein, crotonaldehyde, and cinnamaldehyde, respectively, over 5% Os-C catalyst both with and without solvent.63... 

Preparation.—Ruthenium may be conveniently prepared from osmiridium, which is an alloy of osmium and iridium containing small proportions of rhodium and ruthenium, the last nanjed amounting in some cases to 6 per cent, (see analyses, p. 208). 

As obtained in this way the metal is not pure, but contains small quantities of alloyed elements such as osmium and iridium. 

McCormick [5] prepared thiol-stabilized nanoparticles containing gold, platinum, palladium, rhodium, ruthenium, osmium, and iridium, which were used in optics, immunodiagnostics, and electronics. 

Ruthenium, osmium and iridium hydrides insert N,N -di-p-tolylcarbodiimide into the metal-hydrogen bonds to give N,N -p-tolylformamidinato derivatives. ... 

Some ruthenium, osmium and iridium metal hydrides react with diarylcarbodiimides to give products containing N,N -diarylformamidinate ligands. ... 

Figure 8. Polyhedral hybrid representation of Osmium and Iridium carbonyl clusters.

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