Model Studies of Migratory Insertion in the Ir System

As Forster had noted, migratory insertion in [IrMe(CO)2l3] in nonpolar solvents such as PhCl was slow, even at elevated temperature in the presence of CO, while the corresponding Rh species undergoes migratory insertion spontaneously at room temperature, (Eq. (24)). 

The rate for the Ir reaction was measured at temperatures up to 120 °C and CO pressures up to 6 bar in PhCl by IR using a cylindrical internal reflectance cell 

The same reactions were followed by HP NMR using selective CO and C-Mel labeling. The HPNMR results taken with the IR data suggest that it is the fac, cis isomer of [Ir(C(0)Me)(C0)2l3] which forms initially at 25 °C in CH2Cl2/MeOH and that this partially isomerizes to the mer,trans isomer on heating. Both isomers are formed in broadly equal amounts in the higher temperature reaction in PhCl 

The results above are consistent with the original proposal of Eorster on the importance of the formation of intermediate neutral, possibly reduced coordination num- 

The reaction of Inl3 with [IrMe(CO)2l3] was found to be a convenient route to the synthesis of [IrMe(CO)2l2] whereby the pure compound could be isolated as a dimer [IrMe(CO)2l2]2, (Eq. (29)). 

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