High-Temperature Single-Site Ethylene Polymerization Behavior of Titanate Complexes Supported by 1,3-Bis(3,5-dialkylpyrazol-1-yl)propan-2-olate Ligation

Titanate(1−) complexes Na[(THF)(κ¹-O-bdbpzp)TiCl₄] (1) and Na[(THF)(κ¹-O-bdmpzp)TiCl₄] (2) and titanate(2−) complexes [Na(THF)]₂[(κ¹-O-bdbpzp)₂TiCl₄] (4) and [Na(THF)]₂[(κ¹-O-bdmpzp)₂TiCl₄] (5) were obtained in good yield from reaction of Na[bdbpzp] or Na[bdmpzp] (sodium salt of 1,3-bis(3,5-di-tert-butylpyrazol-1yl)propan-2-ol or 1,3-bis(3,5-dimethylpyrazol-1yl)propan-2-ol) with TiCl₄ (in the appropriate molar ratio) at 0−25 °C. Protonolysis of TiCl₄ with 1 equiv of bdmpzpH furnished related zwitterionic titanate(1−) complex 3 that possessed a κ²-N,O-coordinated pyrazolyl-alkoxide with pendant pyrazolium group. Methylalumoxane (MAO) activation of 1−5 under high-temperature solution polymerization conditions produced active single-site ethylene polymerization catalysts that exhibit considerably higher thermal stability (especially 2/MAO, 3/MAO, and 5/MAO) than previously reported for Cp₂TiCl₂/MAO or Ti catalysts supported by related heteroscorpionate or scorpionate ligation.