The adsorption of chromocene and ferrocene on silica: A solid-state NMR study

Ferrocene and chromocene can be adsorbed on silica surfaces by impregnation or by grinding powders of the metallocenes with silica. The vanishing crystal lattice and formation of mobile surface species can in both cases be proven by diminished Chemical Shift Anisotropies and reduced residual linewidths as well as changes in the chemical shifts of the 1H and 13C MAS NMR signals. In contrast to adsorbed ferrocene, the surface-adsorbed chromocene is highly air-sensitive and continues to react with the silica surface within an hour.