Titanium and Zirconium Permethylpentalene Complexes, Pn*MCp^RX, as Ethylene Polymerization Catalysts

Abstract

Me), have been synthesized and fully characterized by multi-nuclear NMR spectroscopy, elemental analysis, and single crystal X-ray diffraction studies. These complexes were immobilized on an insoluble polymethylaluminoxane (sMAO), MAO-modified silica (ssMAO) and a MAO-modified layered double hydroxide (LDH-MAO). The effect of substitution around the Cp ligand was examined in relation to their performance (activity, M w , PDI, morphology) for ethylene polymerization measured both in solution and in slurry phase. Maximum solution-phase activities of 3585 kg/mol.h.bar were recorded at modest [Zr]:[Al] ratios of 1:250. These were compared to the activities recorded using the equivalent solid supported complexes, we observed that sMAO was a superior support material with average increases in activity of 5.3 and 2.3 times relative to ssMAO and LDH-MAO respectively. Most striking was the observation that slurry-phase ethylene polymerization activities using equivalent pro-catalysts supported on sMAO showed enhanced performance compared to the solution phase up to a maximum of 4486 kg/mol.h.bar.

Ring-opening polymerisation of l- and rac-lactide using group 4 permethylpentalene aryloxides and alkoxides

“…This splitting pattern is consistent with molecules of C s symmetry and has been reported previously for Pn*TiCl(OAr) and Pn*ZrCp R (Cl) complexes. 44,47 The cyclopentadienyl protons are observed as singlets at approximately 5.6 ppm, with other features of the -OR groups present as expected; a singlet at 1.19 ppm for O t Bu, a singlet at 2.05 ppm, a triplet at 6.81 ppm and a doublet at 7.18 ppm for O-2,6-Me-C 6 H 3 , and doublets at 1.21 and 1.33 ppm, a septet at 2.93 ppm, a triplet at 6.97 ppm and a doublet at 7.17 ppm for O-2,6-i Pr-C 6 H 3 .…”

“…42,43 In addition, we recently reported a new family of chiral group 4 alkoxide and aryloxide half-sandwich η 5 -complexes of a chiral cyclopentadienyl-derived (hydro)permethylpentalenyl ligand {(C 8 Me 6 H)ML 3 ; Pn*(H)ML 3 } as very active initiators for the ROP of L-and rac-lactide. 56 Herein, following on from our work on Pn*MX 2 , 44,45 we report the development of a new family of group 4 η 8 -permethylpentalenyl complexes of the type {(η 8 -C 8 Me 6 )ML 2 ; Pn*ML 2 } (Chart 2) as initiators for the ROP of L-and raclactide. By targeting Pn*ML 2 complexes the stereoelectronic properties of the ancillary ligands and initiation groups can be varied to influence polymerisation activity and stereocontrol.…”

Zirconium arene triple-decker sandwich complexes: synthesis, electronic structure and bonding

“…, Pn*), 24 in particular that of the group 4 metals (Ti, Zr and Hf) in the context of small molecule activation 25 and ethylene polymerisation catalysis. [26][27][28] Herein, we report the synthesis and characterisation of a series of triple-decker sandwich complexes of zirconium which feature the Z 8 -Pn* ligand and a m-Z 6 :Z 6 -bridging arene.…”

Controlling the Surface Hydroxyl Concentration by Thermal Treatment of Layered Double Hydroxides

“…Utilizing 1 H and 27 Al solid-state MAS NMR and FTIR spectroscopy, Peng and co-workers have investigated the thermal decomposition of a series of MgAl-X LDHs (X = NO3, CO3, Cl and ClO4) with varying Mg:Al ratios. 20 In all cases, after dehydration (up to 150 °C), dehydroxylation of Mg2AlOH groups and formation of four coordinate aluminum ions occurred at lower temperatures than dehydroxylation of Mg3OH groups.…”

“…Amongst other applications, our group has looked at utilizing these materials as solid supports for catalysis, mainly ethylene polymerisation. [24][25][26][27][28] As the temperature of dehydroxylation was increased the initial white powder appeared greyer and darker which may be due to incomplete combustion of the AMO solvent.…”