Interaction of Metallocenes with Oxidic Surfaces

By interaction from the gas phase of metallocenes, MCp2, (M = Mg, Fe, Cr) with the surface OH groups of highly dehydroxylated silica, a reaction occurs leading to the formation of C5H6 and anchored -SiOMCp species. The reaction is quantitative with MgCp2, but occurs to a lower extent with CrCp2 (due to the formation of a clustered species) and with FeCp2 (due to the high stability of this molecule). The anchored complexes of Cr react with CO at RT to give well defined neutral and negatively charged polycarbonylic compounds. Similar reactions are not observed with MgCp2 and FeCp2. MgCp2, FeCp2 and CrCp2 penetrates into the Na-Y zeolite channels and cavities without any substantial perturbation of their IR spectra. By addition of CO at RT to presorbed CrCp2 the slow formation of [CpCr(CO)3]- anions is observed. The IR spectra of these anionic species are similar to those observed for CO on the CrCp2/SiO2 system.