Structure-reactivity relationship in silacycloalkyl diamide complexes of titanium(IV)

The structure-reactivity relationship of titanium complexes CySi(HNBu ')(2) TiCl2 (1) (CySi = silacyclobutane, silacyclopentane, silacyclopentene, and silacyclohexane) stabilized by a series of cyclic silyldiamide ligands has been studied. The crystallographic results establish that steric interactio ns between the silacycloalkyl and tort-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 diamid e complexes (la and 1b) exhibit low ethylene polymerization activity (3.9 s imilar to5.8 kg PE mol(cat) (-1)h(-1)) in the presence of methylalumoxane. highly puckered silacyclohexyl diamide complex lc shows better activity (10 kg PE mol(cat) h(-1)) for the ethylene polymerization when it is activated with MAO.