IR spectroscopy has been used to study the interaction of silica with PhNEt2 (N) and B(C6F5)(3) (B) and subsequent interaction of the support SiO2/[N + B] with dimethylzirconocene Me2Si(2-Me-Ind)(2)ZrMe2 ("Zr"). The data were obtained on the composition of the surface compounds appeared at both stages of catalyst synthesis. It has been shown that (B) and (N) interact with OH groups of silica to form ionic pair [H-NR3](+)[(C6F5)(3)B-O-Sidrop](-) (IP-1). Cation fragment of this pair contains highly reactive N-H bond with a.b. at 3230 cm(-1). It has been found that N-H groups in a part of IP-1 complexes react with neighboring OH groups of silica by hydrogen bonding that gives complexes IP-2. It has been shown that "Zr" complexes interact both with complexes IP-1 and IP-2. As "Zr" reacts with IP-1, zirconium ionic complexes IP-3 containing Zr-Me bond are formed on silica. These complexes are suggested to be the precursor of the polymerization active sites. The reaction of "Zr" with IP-2, most likely, produces surface zirconium compound containing no Zr-Me bonds and inactive for propylene polymerization. (C) 2004 Elsevier B.V. All rights reserved.