An investigation of catalyst/cocatalyst/support interactions in silica-supported olefin polymerization catalysts based on Cp*TiMe3*

Some of the interactions in an organometallic catalyst/cocatalyst/support material have been studied quantitatively (by analysis of volatiles and surface organometallic fragments) and spectroscopically (by IR, 13C and 29Si solid state CP/MAS NMR). The initial product of grafting Cp*TiMe3 onto an Aerosil silica is the supported organometallic complex ≡SiOTiCp*Me2, 1, which is thermally unstable. Mild heating generates the supported tetramethylfulvene complex ≡ SiOTiFv*(Me), 3, via an intramolecular C–H activation process. Grafting of AlMe3 onto either 1 or 3 yields a methylene-bridged heterobinuclear complex, (≡SiO)2Cp*TiCH2AlMe2, 5, and is accompanied by extensive methylation of the silica surface. The direct reaction of AlMe3 with the unmodified silica leads predominantly to the supported organometallic fragment ≡ SiOAl2(CH3)3(CH2), 6, whose proposed structure includes a bridging methylene and a bridging siloxide ligand. Its reaction with Cp*TiMe3 generates methane and ≡ SiOAl2(CH2)2TiCp*Me4, 7.