Iridium carbonyl halides

Alkali halides react with [Ir(CO)3(PPh3)2]+ to form iridium carbonyl halides Ir(CO)(PPh3)2Cl or Ir(CO)2(PPh3)2I (193). 

The cationic complexes [Ir(CO)2(SbPh3)3]+ and [Ir(CO)2(PR3)2]+ (R = Ph, C6Hn) have been synthesized from iridium carbonyl halide derivatives with halogen acceptors in the presence of CO.109... 

Cobalt carbonyl halides, in contrast to rhodium and iridium carbonyl halides, are very unstable, and only few have been prepared and investigated [CoX(CO)4] is... 

Rhodium and iridium carbonyl halides are easily formed from [MX ] or MX3 by the action of CO, most commonly in solutions, although in some cases these compounds may be obtained in the solid state under atmospheric pressure of CO ... 

Rhodium and iridium carbonyl halides are also prepared from organic compounds, for example, anhydrous HCOOH and DMF, which decompose with carbon monoxide evolution. The following rhodium carbonyl halides are known [Rh2X2(CO)4], [RhX2(CO)2] - (X = Cl, Br, I), [Rh2X4(CO)2] (X = Br, I), [RhX3(CO)],... 

A particularly interesting case is that of the platinum metal group which, in addition to platinum (Pt), comprises ruthenium (Ru), osmium (Os), rhodium (Rh), iridium (Ir), and palladium (Pd). These carbonyl halides are usually the most practical precursors for metal deposition because of their high volatility at low temperature. Indeed two of them, palladium and platinum, do not form carbonyls but only carbonyl halides. So does gold. 

These early successes with carbonyl complexes of rhenium encouraged me to undertake systematic research on the carbon monoxide chemistry of the heavy transition metals at our Munich Institute during the period 1939-45, oriented towards purely scientific objectives. The ideas of W. Manchot, whereby in general only dicarbonyl halides of divalent platinum metals should exist, were soon proved inadequate. In addition to the compounds [Ru(CO)2X2] (70), we were able to prepare, especially from osmium, numerous di- and monohalide complexes with two to four molecules of CO per metal atom (29). From rhodium and iridium (28) we obtained the very stable rhodium(I) complexes [Rh(CO)2X]2, as well as the series Ir(CO)2X2, Ir(CO)3X, [Ir(CO)3]j (see Section VII,A). With this work the characterization of carbonyl halides of most of the transition metals, including those of the copper group, was completed. 

Studies on the carbonyl halides of the noble metals led us directly to the discovery of the pure carbonyls of these elements. Especially impressive was the formation of tetranuclear iridium tricarbonyl, [Ir(CO)3]4, via the tricarbonyl chloride Ir(CO)3Cl, as demonstrated by the simultaneous... 

The following metal compounds are used for the preparation of the catalysts oxides, metal carbonyls, halides, alkyl and allyl complexes, as well as molybdenum, tungsten, and rhenium sulfides. Oxides of iridium, osmium, ruthenium, rhodium, niobium, tantalum, lanthanum, tellurium, and tin are effective promoters, although their catalytic activity is considerably lower. Oxides of aluminum, silicon, titanium, manganese, zirconium as well as silicates and phosphates of these elements are utilized as supports. Also, mixtures of oxides are used. The best supports are those of alumina oxide and silica. 

Catalysis. Iridium compounds do not have industrial applications as catalysts. However, these compounds have been studied to model fundamental catalytic steps (174), such as substrate binding of unsaturated molecules and dioxygen oxidative addition of hydrogen, alkyl halides, and the carbon—hydrogen bond reductive elimination and important metal-centered transformations such as carbonylation, p-elimination, CO reduction, and... 

The products of oxidative addition of acyl chlorides and alkyl halides to various tertiary phosphine complexes of rhodium(I) and iridium(I) are discussed. Features of interest include (1) an equilibrium between a five-coordinate acetylrhodium(III) cation and its six-coordinate methyl(carbonyl) isomer which is established at an intermediate rate on the NMR time scale at room temperature, and (2) a solvent-dependent secondary- to normal-alkyl-group isomerization in octahedral al-kyliridium(III) complexes. The chemistry of monomeric, tertiary phosphine-stabilized hydroxoplatinum(II) complexes is reviewed, with emphasis on their conversion into hydrido -alkyl or -aryl complexes. Evidence for an electronic cis-PtP bond-weakening influence is presented. 

Binding energy, pentacarbonyliron, 6, 3 Binuclear complexes bis-Cp titanium halides, 4, 522 with Ni-M and Ni-C cr-bonds heterometallic clusters, 8, 115 homometallic clusters, 8, 111 Binuclear dicarbonyl(cyclopentadienyl)hydridoiron complexes, with rand C5 ligands, 6, 178 Binuclear iridium hydrides, characteristics, 7, 410 Binuclear monoindenyl complexes, with Ti(IV), 4, 397 Binuclear nickel(I) carbonyl complexes, characteristics, 8, 13 Binuclear osmium compounds, with hydrocarbon bridges without M-M bonds, 6, 619... 

Alternatively, mild carbonylation of an iridium halide may be used (39). 

The dimeric hydrido complex [Ir(H)(X)2(CO)(PR3)]2 (X = Cl, Br PR3 = PEt3, PPh3) has been synthesized by carbonylation of iridium halides followed by phosphine addition the complex... 

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