Iridium sulfides

Rufus IB, Viswanathan B, Ramakrishnan V, Kuriacose JC (1995) Cadmium sulfide with iridium sulfide and platinum sulfide deposits as a photocatalyst for the decomposition of aqueous sulfide. J Photochem Photobiol A 91 63-66... 

Binary Compounds. The fluorides of indium are IrF [23370-59-4] IrF [37501-24-9] the tetrameric pentafluoride (IiF ) [14568-19-5], and JIrFg [7789-75-7]. Chlorides of indium include IrCl, which exists in anhydrous [10025-83-9] a- and p-forms, and as a soluble hydrate [14996-61-3], and IrCl [10025-97-5], Other haUdes include IrBr [10049-24-8], which is insoluble, and the soluble tetrahydrate IrBr -4H20 IrBr [7789-64-2]-, and Irl [7790-41-2], Iridium forms indium dioxide [12030-49-8], a poorly characteri2ed sesquioxide, 11203 [1312-46-5]-, and the hydroxides, Ir(OH)3 [54968-01-3] and Ir(OH) [25141-14-4], Other binary iridium compounds include the sulfides, IrS [12136-40-2], F2S3 [12136-42-4], IrS2 [12030-51 -2], and IrS3 [12030-52-3], as well as various selenides and teUurides. 

More than 200 ores are known to contain cobalt but only a few are of commercial value. The more important are arsenides and sulfides such as smaltite, C0AS2, cobaltite (or cobalt glance), CoAsS, and linnaeite, C03S4. These are invariably associated with nickel, and often also with copper and lead, and it is usually obtained as a byproduct or coproduct in the recovery of these metals. The world s major sources of cobalt are the African continent and Canada with smaller reserves in Australia and the former USSR. All the platinum metals are generally associated with each other and rhodium and iridium therefore occur wherever the other platinum metals are found. However, the relative proportions of the individual metals are by no means constant and the more important sources of rhodium are the nickel-copper-sulfide ores found in South Africa and in Sudbury, Canada, which contain about 0.1% Rh. Iridium is usually obtained from native osmiridium (Ir 50%) or iridiosmium (Ir 70%) found chiefiy in Alaska as well as South Africa. 

A few of the transition metals, including gold, platinum, and iridium, are found in nature as pure elements, but most of the others are found associated with either sulfur or oxygen. Iron, manganese, and the metals of Groups 3 to 6 (except for Mo) are most often found as oxides less often, they occur as sulfates or carbonates. Molybdenum and the metals of Groups 7 to 12 (e.xcept forMn and Fe) are most often found as sulfides. 

Ruthenium(ll) sulfide, RuS2 (laurite) iridium(III) sulfide, It2S3 iridium(IV) sulfide, IrS2 palladium(ll) sulfide, PdS platinum(II) sulfide, PtS (braggite, cooperite) platinum(lV) sulfide, PtS2. 

In order to get a catalytic cycle it is necessary that the metal sulfide intermediate can react with hydrogen to form the reduced metal complex (or compound) and H2S. For highly electropositive metals (non-noble metals) this is not possible for thermodynamic reasons. The co-ordination chemistry and the oxidative addition reactions that were reported mainly involved metals such as ruthenium, iridium, platinum, and rhodium. 

The iridium-catalyzed hydroboration of heteroatom-containing substrates (vinyl sulfides, sulfoxides, sulfones and sulfonates) was examined by Westcottand Baker [43]. These authors observed the selechve formation of the linear boronate ester... 

Insoluble iridium dioxide from the sodium peroxide fusion is dissolved in aqua regia, oxidized with nitric acid, and precipitated with ammonium chloride as impure ammonium hexachloroiridate(IV), (NH4)2IrCl6. To purify this salt, it is necessary to redissolve the compound and precipitate out the impurities as sulfides. Nitric acid and ammonium chloride are again used to produce pure ammonium chloroiridate, which is ignited and reduced with hydrogen to give iridium metal. 

Mechanisms have been suggested for the N-bromosuccinimide (NBS) oxidation of cyclopentanol and cyclohexanol, catalysed by iridium(III) chloride,120 of ethanolamine, diethanolamine, and triethanolamine in alkaline medium,121 and for ruthenium(III)-catalysed and uncatalysed oxidation of ethylamine and benzylamine.122 A suitable mechanism has been suggested to explain the break in the Hammett plot observed in the oxidation of substituted acetophenone oximes by NBS in acidic solution.123 Oxidation of substituted benhydrols with NBS showed a C-H/C-D primary kinetic isotope effect and a linear correlation with er+ values with p = —0.69. A cyclic transition state in the absence of mineral acid and a non-cyclic transition state in the presence of the acid are proposed.124 Sulfides are selectively oxidized to sulfoxides with NBS, catalysed by ft-cyclodextrin, in water. This reaction proceeds without over-oxidation to sulfones under mild conditions.125... 

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