Although in 2008 we reported PHNC complexes of Cp*Ir by direct metalation (JACS 2008  , 130, 13200) a phosphine substituent was necessary on the precursor, occupying one coordination site, and no catalysis was found. In contrast, here we report successful formation of unsupported Cp*Ir-PNHC complexes by direct metalation, thanks not only to proper choice of starting heterocycle (1 ) but also to dramatic solvent effects. Either one (2 ) or two unsupported protic NHC ligands are formed directly from an imidazole derivative on Cp*Ir, where water accelerates reaction dramatically. Moreover, once formed the PNHC complex shows very strong hydrogen-bonding capability, as well as the ability to catalyze hydroamination of secondary aminoalkenes, by way of an intermediate (3 ) not seen before in any hydroamination. Unusual PNHC reactivity appears driven by formation of a hydrogen bond as revealed by 15N NMR chemical shift and IR data, as well as by X-ray diffraction. 

Unsupported protic imidazolylidene (PNHC) complexes of Cp*Ir

248th National Meeting (2014)

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