Iridium chloride synthesis

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... 

In 1988, Tilley and coworkers first succeeded in the synthesis of a ruthenium-silene complex by the reaction of Cp Ru(PR3)Cl with a Grignard reagent, and the structure was confirmed by X-ray crystallography (Eq. 9) [10]. They later synthesized an iridium complex in a similar manner (Eq. 10) [11]. Berry synthesized a tungsten-silene complex by treatment of a tungsten-chloride complex with Mg (Eq. 11) [12]. Although reactions of transition metal-silene complexes with Mel, HX, and MeOH have been reported, little is known about their reactivities [11,12]. 

The synthesis of iridium(lll) alkyl and aryl compounds via nucleophilic displacement is straightforward starting from a suitable L3lrX3 complex with X most commonly being chloride. Chatt and Shaw carried out early work on the syntheses of iridium(III) alkyl complexes showing that fac[lrMe3(PR3)3] (69) could be formed by reaction between... 

The zirconocene bis(arylamido) complex 787 was obtained by the reaction of Cp2ZrCl2 with 2 equiv. of the lithium amide605 (Scheme 195). When the reaction is carried out in a 1 1 ratio, the monoamide zirconocene chloride is generated as the major product. Reaction of in situ-generated Cp 2Zr with 2-(methylmercapto)aniline yields monoamido zirconocene hydride 788, the spectroscopic data of which suggest an interaction between the S atom and the Zr center in this complex. The bis(amido) complex 787 serves as a precursor for the synthesis of amido rhodium and iridium complexes. 

Hexachloroiridates(IV) may be prepared by (i) chlorinating a mixture of iridium powder and an alkali metal chloride (ii) in solution, by the addition of an alkali metal chloride to a suspension of hydrous Ir02 in aqueous HC1 or (iii) by the oxidation of [IrCl ] " by O2 in acidic media. Oxidation by Oj probably occurs via reaction (122), with = + 0.21 V. Fine" has suggested that the reverse of reaction (122) occurs in alkaline media. The black crystalline sodium salt Na2[IrCls] is water soluble, and is the usual starting material for the synthesis of other iridium(IV) coordination complexes. The resonance Raman spectrum of (NBu4)2[IrCle] reveals anomalous polarization of all bands this has been ascribed to Jahn-Teller distortions present in the excited electronic state. The single-crystal electronic spectra of various [IrCl ] " salts have also been reported." ... 

In the present synthesis, the more readily available ammonium hexachloroiridate(IV) is substituted for iridium-(IV) chloride. An alternative synthesis involving preliminary reduction of ammonium hexachloroiridate(IV) to hexachloroiridate(III) with ammonium oxalate has been found to give substantially the same total yield of both isomers, but the amount of cis isomer obtained was about twice that of the trans isomer. ... 

Kawi et al. [4, 60] reported on experiments comparing the iridium carbonyl chemistry in NaY zeolite with that in the more basic NaX zeolite (some of whose basicity should perhaps be attributed to the excess NaOH used in the preparation which was ultimately not washed out). The results showed that the supercages in the NaX zeolite were sufficiently basic to provide an effident medium for the synthesis of anionic iridium carbonyl clusters. When [Ir(CO)2(acac)] in NaX zeolite was treated with CO, it was transformed into [HIr4(CO)n] and then into [Irg(CO)t5]. The anionic carbonyl dusters trapped in the cages were characterized by infrared and EXAFS spectroscopies and could not be extracted from the zeolite by ion exchange with bis(triphenylphosphine)iminium chloride, [PPN][Q], in tetrahydrofuran solution. 

Zhou and collaborators devised a procedure for the synthesis of 2-substituted quinazolines via an iridium-catalyzed hydrogen transfer (Scheme 32) (13RSCA334). Treatment of 2-aminobenzylamines 69 with aryl and alkyl aldehydes and styrene as the hydrogen acceptor in the presence of (pentamethylcyclopentadienyl)iridium (III) chloride dimer in xylene under refluxing conditions afforded the desired products in moderate yields. A base, for example, potassium hydroxide, had to be added when employing benzyl alcohol instead of benzaldehyde to furnish 2-phenylquin-azoline (70) in 61% yield (Scheme 32). 

The photochemistry and photophysics of [Ir(terpy)2], prepared for the first time, and of [Ir(phen)3], allegedly prepared pure for the first time, have been described. Quantum yields, in acetonitrile solution, are reported, and the efiTects of added mercury(II) chloride described. The preparation of [Ir(SSS)Cl3], where SSS = 1,4,7-trithiacyclononane, (71), from hydrated iridium trichloride and ligand normally takes many hours, but this synthesis can be achieved in seconds, and with very high yield, in a microwave... 

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