Bridged 1,2-azaborolyl zirconium complexes:: Heterocyclic analogs of the ansa-zirconocene olefin polymerization catalysts

The reaction of phenylvinylboron chloride (11) with allylethylamine afforded (N-allyl-N-ethylamino)vinylphenylborane (12) which on treatment with 5 mol% Grubbs catalyst gave 1-ethyl-2,5-dihydro-2-phenyl-1H-1,2-azaborole (13). The reaction of 13 with LDA in ether gave lithium 1-ethyl-2-phenyl-1H-1,2-azaborolide (14), which was silylated with Me2SiCl2 to afford 15. Reaction of 15 with CpLi followed by LDA and then ZrCl4 gave bridged compound 9. The reaction of 15 with 14 followed by LDA and then ZrCl4 gave the bridged complex 10. The reaction of 14 with Cp*ZrCl3 gave 8. The X-ray crystal structures of 8, 9, and 10 show that they closely resemble the corresponding zirconocene dichlorides. On activation with excess methylaluminoxane 8, 9, and 10 form active catalysts from the polymerization of ethylene. (c) 2005 Elsevier Ltd. All rights reserved.