Iridium halides

The pattern of iridium halides resembles rhodium, with the higher oxidation states only represented by fluorides. The instability of iridium(IV) halides, compared with stable complexes IrCl4L2 and the ions IrX (X = Cl, Br, I), though unexpected, finds parallels with other metals, such as plutonium. Preparations of the halides include [19] 

All the trihalides are known to have 6-coordinate iridium (except the unknown structure of Irl3). IrF3 has the PdF3 structure a-IrCl3 and IrBr3 have structures of the A1C13 type (Ir—Cl 2.30-2.39 A in the former). 

Ir + 2IrF6 -t-1—— 3IrF4 (red-brown) [20] 2Ir + 5F2 350 380 c 2IrF5 (yellow-green) 

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

Rhodium and iridium halides have been shown to react with n-propyldiphenyl-arsine (L = AsPrnPh2) in hot alcoholic media containing the appropriate HX to yield [MX3L3] (M = Rh or Ir X = Cl or Br).208 These compounds undergo a variety of reactions which are summarized in Scheme 13. Structures were assigned using i.r. and 2H n.m.r. spectroscopy. 

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... 

Rhodium and iridium halides, ( / -C5Me5)2MCl4, give ( -C5Me5)2M(H)2(SnR3)2 with RjSnH. 

Another early report of this class of reactions was by Vaska, showing that iridium halides, in the presence of triphenylphosphine, abstract CO from alcohols to give IrCl(CO)(PPh3)2. Dimethylformamide is also decarbonylated by this reaction scheme. Similarly, OsBr2(PPh3)3 reacts with alcohols to yield OsHBr(CO)(PPh3)3 and the corresponding alkane. 

Moreover, even palladium, platinum and iridium halides are used as catalysts, with various phosphorous 111) derivatives as ligands. 

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