Structure-Reactivity Relationship in Silacycloalkyl Diamide Complexes of Titanium(IV)

Abstract

The structure-reactivity relationship of titanium complexes CySi(HNBu^t)₂TiCl₂ (1) (CySi = silacyclobutane, silacyclopentane, silacyclopentene, and silacyclohexane) stabilized by a series of cyclic silyldiamide ligands has been studied. The crystallographic results establish that steric interactions between the silacycloalkyl and tert-butyl groups influence the C(Bu^t)-N-Ti angles and, hence, the steric environment at titanium. The compounds 1 were further investigated as potential catalysts for the polymerization of ethylene. While sterically less demanding silacyclobutyl and -pentyl diamide complexes (1a and 1b) exhibit low ethylene polymerization activity (3.9 ∼5.8 kg PE mol_cat ⁻¹h⁻¹) in the presence of methylalumoxane, highly puckered silacyclohexyl diamide complex 1e shows better activity (10 kg PE mol_cat ⁻¹ h⁻¹) for the ethylene polymerization when it is activated with MAO.

Keywords::

• Cyclic silyldiamide
• silacycloalkane
• titanium
• ethylene polymerization