Iridium carbonyl phosphine

Wickman and Silverthom [276] have investigated bond properties in molecular adducts of the planar Vaska type compound frans-h s(triphenyl-phosphine)iridium carbonyl chloride, IrCl(CO) ((C6H5)3P)2, with small molecules such as H2, O2, CI2, I2, CH3I, and HCl. They essentially observed a decrease of the isomer shift in the following series of adduct molecules XY H2 > HCl > CH3J > O2 > I2 > CI2,... 

Several systematic experimental and computational studies have compared the sigma-donating abilities of NHCs and tertiary phosphines for a variety of transition-metal complexes [8-17]. As illustrative examples, analyses of the nickel-carbonyl complex 1 and iridium carbonyl complex 2 (Fig. 1) re-... 

Among the complexes which may function in this way are pentacyano-cobaltate ion, iron pentacarbonyl, the platinum-tin complex, and iridium and rhodium carbonyl phosphines. It has been suggested that with tristriphenylphosphine Rh(I) chloride, a dihydride is formed and that concerted addition of the two hydrogen atoms to the coordinated olefin occurs (16). There are few examples of the homogeneous reduction of other functional groups besides C=C, C=C, and C=C—C=C penta-cyanocobaltate incidentally is specific in reducing diolefins to monoolefins. 

Scheme 3 Phosphine-modified iridium carbonyl equilibria.

Iridium(I) dithiocarbamate complexes have been the subject of a paper by Duckett and co-workers (1451). Reaction of NaS2CNEt2 with [lr(cod)(p-Cl)]2 gives [lr(S2CNEt2)(cod)] from which a range of carbonyl, phosphine, and phosphite complexes are readily prepared via displacement of the diolefin, some of which exhibit luminescence in fluid solution at room temperature. Benzene solutions of [lr(S2CNEt2) P(OPh)3 2] are unstable and result in slow formation of the ortho-metalated iridium(lll) hydride, [IrH(S2CNEt2) P(0Ph)3 P(0Ph)20CeH4 ] (Eq. 140), characterized by a hydride resonance at 8 -16.02. 

Bis-[triphenylphosphin]-carbonyl-organo-rhodium(0) bzw. -iridium(O) sind aus den entsprechenden Dichloro-Komplexen bzw. Carbonyl-tris-[triphenyl-phosphin]-rhodium(0) bzw.-iridium(O) aus den Chloro-Komplexen zuganglich7 ... 

Two other publications on Ir (73 keV) Mossbauer spectroscopy of complex compounds of iridium have been reported by Williams et al. [291,292]. In their first article [291], they have shown that the additive model suggested by Bancroft [293] does not account satisfactorily for the partial isomer shift and partial quadrupole splitting in Ir(lll) complexes. Their second article [292] deals with four-coordinate formally lr(l) complexes. They observed, like other authors on similar low-valent iridium compounds [284], only small differences in the isomer shifts, which they attributed to the interaction between the metal-ligand bonds leading to compensation effects. Their interpretation is supported by changes in the NMR data of the phosphine ligands and in the frequency of the carbonyl stretching vibration. 

Spogliarich et al. published the details of a study [15] on the electronic effect implicated in reactions catalyzed by iridium/phosphine systems, and found there to be a slight dependence on the charge distribution around the carbonyl group of the substrates, while electron-withdrawing groups enhance the reduction rate... 

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