Preparation of octahydro- and tetrahydro-[1,10]phenanthroline zirconium and hafnium complexes for olefin polymerization

Abstract

Post-metallocenes were constructed for olefin polymerization using 1,2,3,4,7,8,9,10-octahydro[1,10]phenanthroline and 1,2,3,4-tetrahydro[1,10]phenanthroline derivatives. A series of zirconium complexes – LZrCl₂(NHMe₂)₂ [L = 2,9-H₂-C₁₂H₁₂N₂ (4), 2,9-Me₂-C₁₂H₁₂N₂ (5), 2,9-nBu₂-C₁₂H₁₂N₂ (6), and 2,9-iPr₂-C₁₂H₁₂N₂ (7)] – and hafnium complexes – LHfCl₂(NHMe₂)₂ [L = 2,9-H₂-C₁₂H₁₂N₂ (8), 2,9-Me₂-C₁₂H₁₂N₂ (9), 2,9-nBu₂-C₁₂H₁₂N₂ (10), and 2,9-iPr₂-C₁₂H₁₂N₂ (11)] – were synthesized via the reaction of octahydro[1,10]phenanthrolines (2,9-R₂-C₁₂H₁₂(NH)₂) with (Me₂N)₂MCl₂ (DME). The reaction of 2,9-R₂-C₁₂H₁₂(NH)₂ with (PhCH₂)₂ZrCl₂ in the presence of a small amount of THF afforded a series of THF adduct analogs, i.e., LZrCl₂(THF)₂ [L = 2,9-H₂-C₁₂H₁₂N₂ (12), 2,9-Me₂-C₁₂H₁₂N₂ (13), 2,9-nBu₂-C₁₂H₁₂N₂ (14), and 2,9-iPr₂-C₁₂H₁₂N₂ (15)]. The treatment of 12 and 13 with excess Me₃Al resulted in the formation of unexpected complexes, i.e., (η⁴-LAlMe₂)ZrCl₂(Me) [L = 2,9-H₂-C₁₂H₁₂N₂ (16) and 2,9-Me₂-C₁₂H₁₂N₂ (17)], in which the Me₂Al unit forms a five-membered ring through binding with the two nitrogen donors and the MeCl₂Zr unit slips to an η⁴-binding mode containing the N–C–C–N fragment. The treatment of tetrahydro[1,10]phenanthrolines [2,9-R₂-C₁₂NH₉(NH)] with M(CH₂Ph)₄ afforded tribenzyl zirconium complexes LZr(CH₂Ph)₃ – [L = 2,9-Me₂-C₁₂NH₉N (18) and 2,9-nBu₂-C₁₂NH₉N (19)] – and hafnium complexes – LHf(CH₂Ph)₃ [L = 2,9-Me₂-C₁₂NH₉N (20), 2,9-nBu₂-C₁₂NH₉N (21), and 2,9-iPr₂-C₁₂NH₉N (22)]. The structures of 4, 5, 12, 17, and 22 were elucidated by X-ray crystallography. The newly prepared complexes were screened for ethylene/1-octene copolymerization activity: 12 and 16 were potent catalysts (activities of 74 × 10⁶ g mol-Zr h⁻¹ at ∼120 °C under 30 bar ethylene) for the production of wax-like low-molecular weight polyethylene (M_n: ∼5000), which is widely used in industry.