ИСТИНА

An important class of C1-symmetric heteroarylamido hafnium olefin polymeriza-tion catalysts based on complexes was discovered a while ago. These complexes activated by MAO or BARF exhibit a remarkable combination of activity, isospecificity, and high molecular weight capability at high polymerization temperatures. Supposedly, the trimethyl complexes undergo ortho-methalation under polymerization conditions giving precatalyst (or their cationic derivatives) which includes a 6-membered metallacycle instead of the 5-membered metallocycle. Mechanistic evidence suggests that after activation of precatalyst by MAO or BARF, the following in situ ligand modification via monomer insertion into the Hf-CAr bond of the respective cationic complex occurs. As a result, for example, olefin polymerization catalyst supported by sp3-C donor in 7-membered metallacycle is formed. One more potential route to expand metallacycle is via the insertion of a small molecule bearing a carbon-heteroatom or heteroatom-heteroatom multiple bond into the Hf-CAr bond. In this report, we study the reactivity of heteroarylamido complexes (and their analogues) towards small polar molecules bearing multiple heteroatom-element bonds, as well as catalytic performance of the obtained insertion products in olefin polymerization. It is of particular importance that this late stage modification can allow isolation of a series of pre-catalysts with varied properties from a single starting hafnium complex. Additionally, this study gives an insight into fundamental chemistry of these post-metallocenes including the very first stage of insertion of α-olefins into the Hf-CAr bond.