Iridium complexes spectra

This product was characterized by its NMR spectrum and also by reaction with HC1 followed by BF3/methanol to yield methylcyanoacetate ester. The reaction occurs readily, and in the absence of detectable amounts of the oxidative addition product of acetonitrile with the iridium complex, [Hlr-(depe)2CH2CN]+. In contrast, neither Rh(depe)2Cl nor Rh(dmpe)2Cl (dmpe = Me2PCH2CH2PMe2) react with C02 in acetonitrile, though Rh(dmpe)2Cl does react with C02 in nitromethane to form the analogous nitro-acetate hydride complex, (57). 

The rhodium complex displays a 31 P H nmr spectrum that is a doublet in fast exchange and an A2B3X spin system in slow exchange. The iridium complex displays a single line in fast exchange and an A2B3 spin system in slow exchange.4a,4b... 

Parameters for some fluoroacyliridium complexes are listed in Table X. (95) The spectrum of CF2HCOCo(CO)3P(OPh)3 is described as a doublet, 2/(F-H) 57 Hz, 6-71 ppm from CF3C02Me. (96) A shift of 67 1 ppm from CF3C02Me would give 8 = -141-4, which would be more in accord with the iridium complexes. 

Fig. 10.16. Partial LT-FAB mass spectrum of the reaction mixture containing the iridium complexes 1 and 2 in toluene. In addition to the changes in mass, the isotopic pattern changes upon exchange of Cl by Br. By courtesy of P. Hofmann, Heidelberg University.

The peaks in the m/z 50-57 range of the 1-butene El spectrum could be misinterpreted as a complex isotopic pattern if no formula were available on the plot (Fig. 3.8). However, there is no element having a comparable isotopic pattern and in addition, all elements exhibiting broad isotopic distributions have much higher mass. Instead, the 1-butene molecular ion undergoes H, H2 and multiple H2 losses. The m/z 57 peak, of course, results from In a similar fashion the peaks at m/z 39 and 41 appear to represent the isotopic distribution of iridium, but this is impossible due to the mass of iridium (cf. Appendix). However, these peaks originate from the formation of an allyl cation, CsHs, m/z 41, which fragments further by loss of H2 to form the CsHs" ion, m/z 39 (Chap. 6.2.4). 

The methyl(tetrafluoroborato)iridium(III) complex is an air and moisture sensitive white crystalline solid, soluble in dichloromethane. The IR spectrum (in Nujol) shows absorptions at 2070 (vc0), 310 (vIrC1) and 1136, 908cm-1... 

---