Iridium monovalent complexes

The transition-metal catalyzed decomposition of thiirene dioxides has been also investigated primarily via kinetic studies103. Zerovalent platinum and palladium complexes and monovalent iridium and rhodium complexes were found to affect this process, whereas divalent platinum and palladium had no effect. The kinetic data suggested the mechanism in equation 7. 

However, whereas in solution, rhodium catalysts were shown to be the most active, in zeolites, iridium appeared to be an order of magnetitude more active than rhodium. Moreover, CH3CI could be used as the promoter while it could not be in solution. This is due, probably, to the fact that this molecule is strongly polarized by the electrostatic field and, possibly, to the modification of the redox properties of the monovalent precursor complex. This hypothesis was confirmed by the observation that the Si/Al ratio has a large influence on the activity of the rhodium complex (66). 

The structure and dynamics of Rh(77 -C3H5)3 were studied by DFT analysis. The chemistry of Ir(77 -allyl)3 and Rh( j -allyl)3 was compared. While addition of phosphorus ligands such as P(OPh)3 to Rh( 7 -allyl)3 gave monovalent Rh( j -allyl)L, the iridium analog provided stable mixed sigma/pi-tris(allyl) complexes, as evidenced by the structural characterization of mono-, bi-, and tridentate ligand complexes. The addition of CO also provided substantial differences, as shown in Scheme 56. ... 

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