This invention describes novel blocked mercaptosilanes wherein the hydrogen atom of the mercaptan functionality has been substituted. The invention includes methods of preparation for the blocked mercaptosilicon compounds as well as their use in filled rubbers. The blocked mercaptosilanes described are unique in that they allow the mixing of fillers with organic polymers to proceed while remaining inert toward coupling to the polymer. The coupling reactions of these blocked mercaptosilicon compounds are triggered by addition of an appropriate deblocking agent.