THE REACTIONS OF SILYLENES ON THE CHEMICALLY ACTIVATED SILICA SURFACE

The reactions of silylene centres (SC) on the surface of a chemically activated silica (reactive silica, RSi), characteristic of silylenes and carbenes under homogeneous conditions, have been explored by IR and luminescence spectroscopy. SC were found to insert into the H-S bond of H2S and the C-S bond of Me(2)S with rate constants of 4.5.10(-17) cm(3).molecule(-1).s(-1) and 8.3.10(-18) cm(3).molecule(-1).s(-1), respectively. The reaction of SC with ethylene oxide proceeds via ring-opening with a further cyclization to give presumably a 5-membered surface siladioxolane heterocycle. The thermal reaction between SC and ethylene is shown to be very slow and not to yield products of addition or insertion. Ethylene appears to quench both fluorescence and phosphorescence of SC with almost gasokinetical quenching constants, but photoreaction between SC and ethylene was not observed.