Iridium Cyclopentadienide Complexes

Strongly coordinating substituents such as amino and thio poison the complex, and a quinoline failed to undergo labeling. More complex compounds such as 157-159 were found to be good substrates tritiation of 158 under the same conditions gave similar results. 

The latter procedure (involving isolation of the organoiridium-substrate complex) is not practical for use in the tritiation of most substrates, but the former may be if deactivation of the complex by polar functional groups is avoided. The regioselectivity that these iridium cyclopentadienide complexes display is largely complementary to those of iridium phosphines and iridium dionates therefore cyclopentadienide complexes could be valuable additions to the repertory. Unfortunately the air-sensitivity of these complexes and their immediate precursors is a hindrance to their use. Further development of this class would be highly desirable. 

Meanwhile, iridium cyclopentadienide complexes have been found to be catalytic in their mediation of exchange of deuterium from H20 (see Section 3.4). 

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There are no reports of the use of iridium cyclopentadienide complexes with tritiated water. Such applications would be expected to have disadvantages similar to RhCl3-3H20 and related systems (Section 3.4.1) in terms of specific activity limits and the possibility of thermal decomposition of substrates, but with the additional uncertainty of its applicability to a range of substrate structures and functions. 

Figure 3.58 Structure of active iridium cyclopentadienide complex regioselectivity of deuterium labeling in model substrates...

Figure 3.59 Application of iridium cyclopentadienide complex-mediated deuterium labeling of more complex substrates...

The square-pyramidal complexes [Ir( n -diene)2(R)] (diene = 2,3-dimethylbuta-1,3-diene, cyclohexa-1,3-diene R = CH2Ph, cyclo-CHis, R = C2H3) have been obtained343 by reaction of [IrCl( n -diene)2l with RLi or RMgX. In the case of the reaction of the bis( n -cyclohexa-1,3-diene) iridium complex [IrCl(T 4-QH8)2] with sodium cyclopentadienide, the bis(t)2-cyclohexa-1,3-diene) iridium complex [CpIr(ii -C6Hg)2] was formed as the initial product and characterised by X-ray diffiraction. 

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