N-Heterocyclic carbenes (NHCs) are a class of stable carbenes that have found increasing use as ligands for transition metal catalysts. We recently reported a series of unsymmetrically substituted NHC ligands that feature a chelating phenoxide moiety appended to one of the NHC N atoms. These ligands are analogous to the salicylaldimine (sal) framework, a common motif in organometallic chemistry that is applied in catalytic organic reactions and olefin polymerization. We present the synthesis of titanium and zirconium olefin polymerization catalysts, supported by chelating �sal like� NHCs. Double deprotonation of the NHC ligand with two equivalents of KHMDS, followed by treatment of the resulting solution with half an equivalent of either TiCl4(thf)2 or ZrCl4 affords the corresponding bis-ligated species 1  and 2  , respectively. As catalysts, they exhibit excellent activity for the polymerization of ethylene and the copolymerization of ethylene with norbornene and 1-octene when activated with MAO in toluene. Figure 1 . Non-Metallocene Ti and Zr Precatalysts.

Bis−ligated titanium and zirconium complexes of chelating N-heterocyclic carbenes

243rd National Meeting (2012)

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