Iridium complex compounds other salts

Few complexes of iridium(V) are known. Before 1965, literature references to TrFq actually refer to IrFs. Reduction of IrFe by H2 at 60 °C gives IrFs at 100°C, further reduction leads to Ir metal. IrFs is a yellow crystalline solid (/u-eff = 1.32 /xb at 296 K) with a tetrameric structure (1). It is moisture sensitive (equation 5). Other iridium(V) compounds include salts of the type (M)[IrF6] (M+ = NO+, K+, Na+, Rb+, Cs+, Ag+, XeF+, Xe2Fn+, CIO2+, CI4+). KIrFe and CsIrFe exhibit temperature-independent paramagnetism. 

Complexes of other metals are used to sensitize emulsions, and some are used to sensitize even further (supersensitize) gold-sensitized emulsions. " Among these are (NH4)2[PtCl4], (NH4)2[PdCl4], (NH4)2[PdCy, K2[IrCl6] and similar compounds with ruthenium and the other halides. Sensitization by iridium salts and complex ions has been reviewed recently. Mechanisms of action of palladium(II) salts and complex ions on gold-sensitized emulsions have been studied. Several phosphine complexes of palladium and platinum, for example (2), are reported to be effective sensitizers, as are many macrocyclic polyamine compounds and their metal complexes,for example the Cu", Ni", Fe " and Rh " chelates of the cyclen ligand, 1,4,7,10-tetraazacyclododecane (3). 

In the CATIVA process the active catalyst is [Ir(CO)2l2]. Ehie to similar chemistry to the Monsanto process the same chemical plant may be used, which makes a retrofitting commercially highly attractive. Initial studies by Monsanto had shown the iridium complex to be a less-active catalyst than the rhodium complex. However, subsequent research showed that the iridium catalyst could be promoted using ruthenium and/or other salts, and this combination leads to a more-active and more-selective catalyst than the rhodium compound. 

Chloro- and other halo- containing carbonyl compounds of iridium may also be synthesized under mild conditions. Unlike [Rh(CO)2Cl]2, [Ir(CO)2Cl] is not obtainable by the direct reaction of an iridium chloride solution with CO. Instead, [Ir(CO)2Cl2]n (48) is obtained in low yields by reaction between IrCl3-H20 and carbon monoxide. The predominant mononuclear compound obtained upon carbonylation of iridium chloride salts is the tricarbonyl [Ir(CO)3Cl] (49), which appears in the sohd state to be a polymeric array consisting of stacking square-planar Ir(CO)3Cl units with short fr-Ir bonds. Even though [Ir(CO)3Cl] is polymeric, it is sublimable and is stiU a convenient source of iridium(I) containing carbon monoxide. (49) will react with a number of nucleophiles to form mononuclear iridium carbonyl complexes. 

A process for the coproduction of acetic anhydride and acetic acid, which has been operated by BP Chemicals since 1988, uses a quaternary ammonium iodide salt in a role similar to that of Lil [8]. Beneficial effects on rhodium-complex-catalyzed methanol carbonylation have also been found for other additives. For example, phosphine oxides such as Ph3PO enable high catalyst rates at low water concentrations without compromising catalyst stability [40—42]. Similarly, iodocarbonyl complexes of ruthenium and osmium (as used to promote iridium systems, Section 3) are found to enhance the activity of a rhodium catalyst at low water concentrations [43,44]. Other compounds reported to have beneficial effects include phosphate salts [45], transition metal halide salts [46], and oxoacids and heteropolyacids and their salts [47]. 

Cobalt(III) complexes of the type [Co(en)2X2] have long been known, and extensively investigated with regard to mechanisms of reactions in these systems. Some years ago it was decided to extend these studies to include analogous compounds of the other members of this triad, rhodium(III) and iridium(III). It was then learned that very few such compounds had been prepared and it was necessary to start the laborious task of the syntheses and characterizations of these desired complexes. Several salts of [Rh(en)2X2] were prepared and the rates of substitution of some of these have been investigated. ... 

This paper reports the syntheses and properties of salts of [Ir(en)2X2], where the X groups are the same or different anionic ligands. When this work was started the only complex of this type that had been reported" was c/s-[Ir(en)2(N02)2] - Kida has recently described the preparation of cis and trans-[Ir(en)2Cl2]Cl. We have repeated his syntheses and also designed new methods to prepare the same complexes as well as other compounds of iridium(III). 

Ruthenium(III), d, is ruthenium s most stable oxidation state and resembles rhodium(III) and iridium(III) more than osmium(III). The salts inelude the halides, hydroxides, and oxides RuCls SHaO is most important because it is a good starting material for other compounds and reacts readily with olefins and phosphines. Complexes of this oxidation state are known with water, eyanide, oxygenated organies, sueh as diketones and earboxylates, pyridines, earbonyls, ey-elopentadienyls, phosphine, and arsine ligands. A notable differenee between ruthenium(II) and ruthenium(III) is the absenee of ruthenium(III) nitrosyl complexes. 

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