Reactions of group IV metallocene dichlorides with modified silica gel surfaces

Reactions of bis(cyclopentadienyl)titanium dichloride, bis(cyclopentadienyl)zirconium dichloride, and bis(cyclopentadienyl)hafnium dichloride with premodified silica gel surfaces were studied. The silica gel surface was pretreated to selectively eliminate nonhydrogen bonded silanols, hydrogen bonded silanols, or bath before reaction. By study of the metallocene reactions with these silicas and unmodified silica gel, it was found that the metallocenes react predominantly with nonhydrogen bonded silanols. Although none of the metallocenes are very reactive with silica as compared to titanium tetrachloride, reactivity increases in the order Cp(2)TiCl(2) < Cp(2)ZrCl(2) < Cp(2)HfCl(2). (C) 1997 Academic Press.