Iridium chloride catalyst

Iridium, carbonylchlorobis(triphenylphosphine) solid state reactions with hydrogen chloride, 1, 470 Iridium, dihalodicarbonyl-, 6, 142 Iridium, hexachloro-catalysts... 

In 1957 (2) platinic, ruthenium, and iridium chlorides were shown to be catalysts leading to very rapid additions, sometimes below room temperature, of many kinds of SiH compounds. These findings initiated much activity, chiefly in industrial research laboratories, in several countries, because they indicated that the manufacture of new organosilicon monomers and many new silicone polymers and copolymers would become commercially practicable for the first time. 

The secondary aryl amine 24 is far less basic than primary or secondary alkyl amines, and does not form the carbamic acid to any detectable extent in the presence of scC02 [31]. Therefore, 24 is extracted readily from the catalyst-containing IL phase, which can be recycled without noticeable loss of activity and selectivity [13]. In fact, it transpires that the active species is more stable towards oxygen in the IL than in organic solvents. Furthermore, the choice of anion of the IL largely controls the performance of the active cationic species, allowing even the use of an otherwise inactive iridium chloride precursor [ Ir(cod)Cl 2] to form in-situ catalysts... 

Reactions of allylic electrophiles with stabilized carbon nucleophiles were shown by Helmchen and coworkers to occur in the presence of iridium-phosphoramidite catalysts containing LI (Scheme 10) [66,69], but alkylations of linear allylic acetates with salts of dimethylmalonate occurred with variable yield, branched-to-linear selectivity, and enantioselectivity. Although selectivities were improved by the addition of lithium chloride, enantioselectivities still ranged from 82-94%, and branched selectivities from 55-91%. Reactions catalyzed by complexes of phosphoramidite ligands derived from primary amines resulted in the formation of alkylation products with higher branched-to-linear ratios but lower enantioselectivities. These selectivities were improved by the development of metalacyclic iridium catalysts discussed in the next section and salt-free reaction conditions described later in this chapter. 

The platinum-catalyzed reaction of alkanes with chlorine leads to alkyl chlorides and alcohols (Table 6, entry 46) with modest rates and conversions [50], Cydooctane can be easily dehydrogenated (Table 6, entry 47) in the presence of a stabilized vinylalkane by use of the neutral rhenium compound ReH7(PR3)2 [51]. By employing an iridium-based catalyst, the photochemical dehydrogenation of methylcydohexane to methylenecyclohexane is performed at room temperature... 

Transition-metal-catalyzed hydrosilylation was first reported in the late 1950s with catalysts based on platinum, ruthenium, and iridium chlorides. For industrial applications, chloroplatinic acid (H PtCl nHjO) has been used extensively and is highly active for this process. This catalyst has become known as Speier s catalyst. This catalyst is spectacularly reactive, as indicated by the low catalyst loading for the reaction in Equation 16.17. A Pt(0) complex containing vinylsiloxane ligands (platinum divinyltetramethyl-disiloxane) shown in Figure 16.1 has also been used frequently in industrial settings as a catalyst for hydrosilylation. Tliis catalyst has become known as Karstedt s catalyst. ... 

The 15 wt.% Co 0.3wt.% Ir/Al203 catalyst precursor used in this work was prepared by incipient wetness impregnation. The AI2O3 support was impregnated with an aqueous solution containing cobalt nitrate and iridium chloride, and dried at 383 K for 5h. The conventional prepared sample was obtained by thermal calcination (673 K for 6h) and... 

Pincer complexes catalyze a variety of other organic reactions [49-51]. Hence, this work is currently being extended to other metals, and other more readily accessible PCP systems. For example, as shown in Scheme 3, lO-Rfs can be converted to the iridium hydride chloride complex 15-Rfs. Closely related dihydride complexes catalyze dehydrogenations of alkanes at high temperatures [52], However, no efforts to develop recoverable catalysts have been reported to date. 

The use of ethylene adduct lb is particularly important when the species added to activate catalyst la is incompatible with one of the reaction components. Iridium-catalyzed monoallylation of ammonia requires high concentrations of ammonia, but these conditions are not compatible with the additive [Ir(COD)Cl]2 because this complex reacts with ammonia [102]. Thus, a reaction between ammonia and ethyl ciimamyl carbonate catalyzed by ethylene adduct lb produces the monoallylation product in higher yield than the same reaction catalyzed by la and [Ir(COD)Cl]2 (Scheme 27). Ammonia reacts with a range of allylic carbonates in the presence of lb to form branched primary allylic amines in good yield and high enantioselectivity (Scheme 28). Quenching these reactions with acyl chlorides or anhydrides leads to a one-pot synthesis of branched allylic amides that are not yet directly accessible by metal-catalyzed allylation of amides. 

The complexes of the composition [ Ir( t-X)(diene) 2], where X = halogen, OH, OMe (e.g. [IrCl(CO)(cod)]) appeared to be very effective catalysts for the hydrosilylation of allyl chloride by trialkoxy- and alkylalkoxy-silanes [22]. Other iridium complexes have been subsequently reported as catalysts for the synthesis of silane... 

II. 5).204,205 Unsupported iridium catalysts have been prepared by reducing an iridium oxide of Adams type at 165°C under a stream of hydrogen206 or by reducing iridium hydroxide, prepared by addition of lithium hydroxide to an aqueous solution of irid-ium(III) chloride, at 80-90°C and 8 MPa H2.204 Unsupported and supported iridium catalysts may also be prepared by reduction of iridium(IV) chloride with sodium boro-hydride.207 It is noted that the catalytic activity of deactivated iridium can be almost completely regenerated by treatment with concentrated nitric acid.205... 

Colloidal iridium readily decomposes hydrogen peroxide solution, the reaction being, as with platinum, mono-molecular the rate of decomposition is approximately proportional to the concentration of catalyst. Alkali does not affect the reaction velocity, but dilute acids accelerate it. Hydrogen sulphide, mercuric chloride, and certain other substances act as poisons.3 Colloidal iridium is less active, however, than platinum. 

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