Abstract
NMR spectroscopy has been exploited to investigate the reactions of Hf(IV) organometallic complexes with trialkylaluminum and dialkylzinc, with the aim of obtaining insights into the elementary steps of coordinative chain transfer polymerization (CCTP). Bis(cyclopentadienyl)hafnium dimethyl (Cp2HfMe2, 1Me2) and [N-(2,6-diisopropylphenyl)-α-(2-isopropylphenyl)-6-(1-naphthalenyl)-2-pyridinemethanaminato]hafnium dimethyl (2Me2) complexes have been chosen as case studies for understanding the differences between poorly performing and highly active CCTP catalysts, in an attempt to assess the effect of the ancillary ligand on the transalkylation rate. 2Me2 was found to react much more quickly with both AlEt3 and ZnEt2 in comparison to 1Me2, mainly due to a remarkably lower activation enthalpy. In addition, while the ethylation rate was found to depend on the nature of the alkylating agent for 1Me2, it does not for 2Me2. This difference in reactivity was observed also in the case of the ion pairs obtained by rea...
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