Titanacalixarenes in hommogeneous catalysis : synthesis, conformation and catalytic activity in ethylene polymerisation
Résumé
Variously substituted titanacalixarenes were synthesised and tested for their performance as catalysts in ethylene polymerisation: p-tert-butylcalix[4]arene was derivatised to afford distal diether p-tert-butylcalix[4]arenes L1–L4, distal dihydroxy-depleted L5, proximal dihydroxy-depleted L6, proximal diether p-tert-butylcalix[4]arene L7, proximal intrabridged disiloxane L8 and proximal monoether L9. (Dichlorotitana)-p-tert-butylcalix[4]arenes 1–8 and (monochlorotitana)-p-tertbutylcalix[4]arene 9 have been successfully synthesised by reacting L1–L4 with TiCl4·2THF or L5–L9 with TiCl4. The structural conformation of complexes 1–9 in solution were determined by 1H NMR, 13C NMR, NOESY and COSY spectroscopic studies. Compounds 2, 3 and 4 have been structurally characterised by single-crystal X-ray diffraction. Upon activation with methylaluminoxane, compounds 1–8 revealed low to moderate activities for the production of high-density polyethylene (HDPE) to ultra-high-molecular-weight polyethylene (UHMWPE). 6/MAO gave the best activity at 770 kgPE (mol Ti)–1 h–1.