Catalytic Activities of the Ir Complexes

In contrast to the various applications of the pincer Rh complexes bearing two NHC moieties, the respective Ir complexes seem to be of interest only for C-H activation reactions so far. 

Although all Ir catalysts presented so far contained Ir in its oxidation state -Fill, the active catalytic species is considered to be an Ir(I) complex formed in situ. 

Within the last years, a variety of Rh and Ir bis(NHC) pincer complexes could be synthesized. After pubUshing the first Rh bis(NHC) pincer complex 32, Peris et al. showed that this complex class is highly valuable for catalytic applications and worth investigating. Although the activity of their complex in transfer hydrogenation of ketones is far less than that of the most active Ru PCP complexes [44], the activity was nevertheless comparable to that of other Rh NHC complexes at that time. 

The Rh CCC pincer complex 36 tested by Hollis in the hydrosilylation of acetylenes shows a high activity and selectivity for the Z-product, which is also found for a bimetalUc NHC complex bearing the same ligand in a bridging 

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