Of osmium compounds

Chemical ingenuity in using the properties of the elements and their compounds has allowed analyses to be carried out by processes analogous to the generation of hydrides. Osmium tetroxide is very volatile and can be formed easily by oxidation of osmium compounds. Some metals form volatile acetylacetonates (acac), such as iron, zinc, cobalt, chromium, and manganese (Figure 15.4). Iodides can be oxidized easily to iodine (another volatile element in itself), and carbonates or bicarbonates can be examined as COj after reaction with acid. 

Fig. 7.54 Mosshauer spectra of osmium compounds obtained at 4.2 K with 69.6 keV (a) and 36.2 keV (b) transitions of Os with a source of Ir in iridium metal (from [258])...

There is much current excitement and activity in the field of homogeneous hydrogenation using ruthenium catalysts. This is reflected in the recent, explosive increase in the number of research publications in this area, now rivaling those for rhodium catalysts (Fig. 3.1). Meanwhile, the price of rhodium metal has risen dramatically, becoming about ten times that of ruthenium, on a molar basis. The number of reports on the use of osmium catalysts has remained low, partly because of the higher price of osmium compounds - about ten times that of ruthenium - and partly because the activity of osmium catalysts is often lower. 

Ammino-derivatives of Osmium Compounds—Ammino-derivatives of Iridium Salts—Derivatives of Iridous, Iridic, and Iridium Sesqui-salts. 

The reaction is carried out in a 100-ml. rocking autoclave capable of withstanding pressures up to 300 atmospheres and operating at maximum temperatures of 300°. Owing to the toxicity of osmium compounds, all manipulations must he carried out in a well-ventilated hood. 

Caution. Osmium(VIII) oxide is extremely toxic. The yellow solid melts at 31° and has an appreciable vapor pressure even at room temperature. The compound is often liberated when solutions of osmium compounds are treated with oxidizing agents. Ample precautions to protect eyes, nose, and mouth are essential. 

Chronic exposure to osmium tetroxide can result in an accumulation of osmium compounds in the liver and kidney and damage to these organs. Osmium tetroxide has been reported to cause reproductive toxicity in animals this substance has not been shown to be carcinogenic or to show reproductive or developmental toxicity in humans. 

Os3(CO)i2 with PPhMe2 and AsPhMc2. Release of the ligand from these complexes was not discussed. In view of the expense of osmium compounds and the complex mixtures produced from these reactions, these complexes are rather unattractive synthetically as benzyne sources. 

Other volatile compounds of elements can be used to transport samples into the plasma flame. For example, hydride reduction of mercury compounds gives the element (Hg), which is very volatile. Osmium can be oxidized to its volatile tetroxide (OSO4), and some elements can be measured as their volatile acetylacetonate (acac) derivatives, as with Zn(acac)2. 

Consequent potentiometric titration of osmium(IV) and laithenium (IV) in their mixtures has been canied out in broad range of concentrations from 1 mkg to 200 mkg in samples of 20 ml. It has been shown the possibility of amperemetric determination of osmium(VI) in binary and triple systems with silver(I), platinum(IV), palladium(II), gold(III), founded on formation of corresponding compounds with dimerkaptotiopiron, having a different solubility. The deteriuination of Os(VI) is possible under tenfold - hundredfold excess of above mentioned metals. 

The extraction of osmium(VI) and osmium(IV) compounds with dimerkaptotiopiron by polar solvents has been resear ched. 50 -100 - multiple concentrating has been carried out in acid solutions regardless from chemical form of Os(VI) and Os(IV) with the following determination of each of them from one sample by amperemetric titration of reextracts by means of DT. A methodic of atom absor ption determination of osmium has been suggested. 

Table 25.3 Oxidation states and stereochemistries of some compounds of iron, mthenium and osmium...

The most interesting oxides of Ru and Os, however, are the volatile, yellow tetroxides, RUO4 (mp 25°C, bp 130°C< 3>) and OSO4 (mp 40°C, bp 130°C). They are tetrahedral molecules and the latter is perhaps the best-known compound of osmium. It is produced by aerial oxidation of the heated metal or by oxidizing other compounds of osmium with... 

A solution of 1.0 g of A -3,11-diketo-20-cyano-21-acetoxy-pregnene in 10 cc of benzene is treated with 1.0 g of osmium tetroxide and 0.43 g of pyridine. After standing at room temperature for 18 hours, the resulting solution is treated successively with 50 cc of alcohol, and with 50 cc of water containing 2.5 g of sodium sulfite. The mixture is stirred for 30 hours, filtered, and the filtrate acidified with 0.5 cc of acetic acid and concentrated to small volume in vacuo. The aqueous suspension is then extracted four times with chloroform, the chloroform extracts are combined, washed with water and concentrated to dryness in vacuo. Recrystallization of the residue from acetone gives 3,11,20-triketo-17(a)-21-dihydroxy-pregnane MP 227° to 229°C. This compound is then treated with acetic anhydride and pyridine for 15 minutes at room temperature to produce 3,11,20-triketo-17(a)-hydroxy-21-acetoxy-pregnane or cortisone acetate. 

Other examples are the use of osmium(VIII) oxide (osmium tetroxide) as catalyst in the titration of solutions of arsenic(III) oxide with cerium(IV) sulphate solution, and the use of molybdate(VI) ions to catalyse the formation of iodine by the reaction of iodide ions with hydrogen peroxide. Certain reactions of various organic compounds are catalysed by several naturally occurring proteins known as enzymes. 

Much less is known about ruthenium oxyhalides than about the osmium compounds. The only compound definitely characterized [24] is RuOF4, synthesized by fluorination of Ru02, condensing the product at -196°C. It loses oxygen slowly at room temperature, rapidly at 70°C. 

Another type of osmium(VI) compound involving multiple bonds can be viewed as a derivative of OsN3+. The nitrides have attracted interest as they are often photoluminescent... 

F.13 Osmium forms a number of molecular compounds with carbon monoxide. One light-vellow compound was analyzed to give the following elemental composition 15.89% C, 21.18% O, and 62.93% Os. (a) What is the empirical formula of this compound (b) From the mass spectrum of the compound, the molecule was determined to have a molar mass of 907 g-mol 1. What is its molecular formula ... 

N-Tosylated P-hydroxy alkylamines (which can be easily hydrolyzed to P-hydroxyamines" ) can be prepared " by treatment of alkenes with the trihydrate of Chloramine-T and a catalytic amount of OSO4. In some cases yields can be improved by the use of phase-transfer catalysis." The reaction has been carried out enantioselectively." In another procedure, certain P-hydroxy secondary alkylamines can be prepared by treatment of alkenes with the osmium compounds... 

Primary (R = H) and secondary aromatic amines react with alkenes in the presence of thallium(III) acetate to give vie- diamines in good yields. " The reaction is not successful for primary aliphatic amines. In another procedure, alkenes can be diaminated by treatment with the osmium compounds R2NOSO2 and R3NOSO (R = t-Bu)," analogous to the osmium compound mentioned at 15-51. The palladium-promoted method of 15-51 has also been extended to diamination. " Alkenes can also be diaminated indirectly by treatment of the aminomercurial compound mentioned in 15-51 with a primary or secondary aromatic amine. 

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