1.3- Dialkyl-4,5-dimethylimidazol-2-ylidene

Likewise, the direct addition of a free NHC to an early transition metal precursor may lead to the corresponding NHC-M adducts. For example, Kuhn et al. reported that the reaction of a free NHC with TiCU leack to the formation of the mono-adduct (NHOTiCU (NHC = l,3-dialkyl-4,5-dimethylimidazol-2-ylidene). A careful hydrolysis of the latter afforded the corresponding NHC p-oxo titanium(IV) complex, which was X-ray characterized [29]. Direct coordination of the free carbene was also used to access various monodentate adducts such as (NHC)2TiF4 [30,31], (NHC)TiCl2(NMe2)2 [32,33], or benzannulated NHC Ti complex (NHC)TiCU [34]. 

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