Iridium complexes bromides

The dihydrido complex [RhH2(ri5-C5Me5)(PMe3)] forms C—H insertion products when irradiated in the presence of alkanes (ethane, propane).227,228 Reaction with CHBr3 leads to bromoalkylrhodium complexes, which on treatment with bromine give ethyl bromide or 1-bromopropane in 70-85% yield. The less stable iridium complex formed with neopentane could not be converted directly to neopentyl bromide.229 It gave, however, a mercury derivative that yielded the bromide after treatment with bromine. 

The iridium(I) halide complexes [IrCl], [IrBr] and [Irl] are believed to exist. Heat treatment (to 1043 K) of [IrCl3] causes sublimation of [IrCl], which decomposes above 1071 K and is insoluble in both alkaline and acidic media.172 [IrBr] may be obtained by heating the iridium(III) bromide to 758 K in an HBr atmosphere. The monobromide complex is stable at lower temperatures, and is slightly soluble in water, in acidic and in alkaline media.173 [Irl] forms upon heating either [Irl2] or [Irl3] to 628 K in an HI atmosphere.173... 

Dry hydrogen bromide and acetyl bromide react with the planar iridium complex (IV) in benzene to form a mixture of two stereoisomers, (IX) and (X) 41). The same mixture of isomers was obtained by adding hydrogen... 

The syntheses and spectroscopic and electrochemical characterization of the rhodium and iridium porphyrin complexes (Por)IVI(R) and (Por)M(R)(L) have been summarized in three review articles.The classical syntheses involve Rh(Por)X with RLi or RMgBr, and [Rh(Por) with RX. In addition, reactions of the rhodium and iridium dimers have led to a wide variety of rhodium a-bonded complexes. For example, Rh(OEP)]2 reacts with benzyl bromide to give benzyl rhodium complexes, and with monosubstituted alkenes and alkynes to give a-alkyl and fT-vinyl products, respectively. More recent synthetic methods are summarized below. Although the development of iridium porphyrin chemistry has lagged behind that of rhodium, there have been few surprises and reactions of [IrfPorih and lr(Por)H parallel those of the rhodium congeners quite closely.Selected structural data for rr-bonded rhodium and iridium porphyrin complexes are collected in Table VI, and several examples are shown in Fig. 7. ... 

The square pyramidal complexes of group 9 iridium cyclopropylbis(>/4-diene) complexes were recently synthesized in poor yields (3-5%) by metathesis reaction between (tf-diene)2 IrCl and cyclopropyllithium or cyclopropylmagnesium bromide (equation 16)45. 

Alkyl- or aryl-iridium(I) complexes IrR(CO)L2 (R = CH3, C6H5 L = PMe3, PMe2Ph) will oxidatively add secondary alkyl bromides or iodides to give octahedrally coordinated bis(alkyl)iridium(III) complexes, as exemplified in Equation 1. 

Numerous phospho-chlorides, phospho-bromides, and other complex derivatives of iridium have been prepared by Geisenheimer.5... 

The corresponding reactions with iridium(I) precursors again behave differently. When the phosphino functionalised imidazolium salt is reacted with [IrlcodlCl], the phosphane adduct with a pendant imidazolium moiety is formed. A similar reaction with the more reactive [Ir(cod)( Li-H)(p,-Cl)2]2 yields a five coordinate iridium(I) complex that might be described as having square pyramidal geometry with the bromide in apical position and the carbene in abnormal coordination mode [47-49] (see Figure 3.97). 

When tin(II) in HBr solution is added to an acidic solution of the iridium bromide complex, a yellow complex is produced on heating. The absorbance of this complex is the basis of the spectrophotometric determination of iridium [70-72]. Maximum colour intensity is obtained by heating the solution for 1 min on a boiling water-bath. If the heating is continued for longer than 2 min the colour intensity decreases. 

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